How loading of file into memory in perl - perl

i have tried with some script for sorting a input text file in descending order and print only top usage customer.
input text file containts:
NAME,USAGE,IP
example :
Abc,556,10.2.3.5
bbc,126,14.2.5.6
and so on, this is very large file and i am trying to avoid loading file into memory.
I have tried with following script.
use warnings ;
use strict;
my %hash = ();
my $file = $ARGV[0] ;
open (my $fh, "<", $file) or die "Can't open the file $file: ";
while (my $line =<$fh>)
{
chomp ($line) ;
my( $name,$key,$ip) = split /,/, $line;
$hash{$key} = [ $name, $ip ];
}
my $count= 0 ;
foreach ( sort { $b <=> $a } keys %hash ){
my $value = $hash{$_};
print "$_ #{$value} \n" ;
last if (++$count == 5);
}
Output should be sorted based on usage and it will show the name and IP for respective usage. " `

I think you want to print the five lines of the file that have the highest value in the second column
That can be done by a sort of insertion sort that checks each line of the file to see if it comes higher than the lowest of the five lines most recently found, but it's easier to just accumulate a sensible subset of the data, sort it, and discard all but the top five
Here, I have array #top containing lines from the file. When there are 100 lines in the array, it is sorted and reduced to the five maximal entries. Then the while loop continues to add lines to the file until it reaches the limit again or the end of the file has been reached, when the process is repeated. That way, no more than 100 lines from the file are ever help in memory
I have generated a 1,000-line data file to test this with random values between 100 and 2,000 in column 2. The output below is the result
use strict;
use warnings 'all';
open my $fh, '<', 'usage.txt' or die $!;
my #top;
while ( <$fh> ) {
push #top, $_;
if ( #top >= 100 or eof ) {
#top = sort {
my ($aa, $bb) = map { (split /,/)[1] } ($a, $b);
$bb <=> $aa;
} #top;
#top = #top[0..4];
}
}
print #top;
output
qcmmt,2000,10.2.3.5
ciumt,1999,10.2.3.5
eweae,1998,10.2.3.5
gvhwv,1998,10.2.3.5
wonmd,1993,10.2.3.5

The standard way to do this is to create a priority queue that contains k items, where k is the number of items you want to return. So if you want the five lines that have the highest value, you'd do the following:
pq = new priority_queue
add the first five items in the file to the priority queue
for each remaining line in the file
if value > lowest value on pq
remove lowest value on the pq
add new value to pq
When you're done going through the file, pq will contain the five items with the highest value.
To do this in Perl, use the Heap::Priority module.
This will be faster and use less memory than the other suggestions.

Algorithm remembering the last 5 biggest rows.
For each row, check with the lowest memorized element. If more - are stored in the array before next biggest item with unshift lowest.
use warnings;
use strict;
my $file = $ARGV[0] ;
my #keys=(0,0,0,0,0);
my #res;
open (my $fh, "<", $file) or die "Can't open the file $file: ";
while(<$fh>)
{
my($name,$key,$ip) = split /,/;
next if($key<$keys[0]);
for(0..4) {
if($_==4 || $key<$keys[$_+1]) {
#keys[0..$_-1]=#keys[1..$_] if($_>0);
$keys[$_]=$key;
$res[$_]=[ $name, $ip ];
last;
}
}
}
for(0..4) {
print "$keys[4-$_] #{$res[4-$_]}";
}
Test on file from 1M random rows (20 Mbytes):
Last items (This algorithm):
Start 1472567980.91183
End 1472567981.94729 (duration 1.03546 seconds)
full sort in memory (Algorithm of #Rishi):
Start 1472568441.00438
End 1472568443.43829 (duration 2.43391 seconds)
sort by parts of 100 rows (Algorithm of #Borodin):
Start 1472568185.21896
End 1472568195.59322 (duration 10.37426 seconds)

Related

identify and insert the missing rows

An array is populated from a tab delimited text (5 column) file that sometimes is missing rows. I need to identify and insert the missing rows. Inserting a string "blank row found" is sufficient.
Here is an example of data from file:
chr1:11174372 MTOR 42939 42939 7
chr1:65310459 JAK1 1948 1948 3
I’ve created an array of elements that identifies the second column of each row that should be present in the file, in the order each row should be present. However, I'm not sure how to continue from here, since I'm unable to install any Perl modules on the server (e.g. Arrays::Utils).
Is comparing arrays the correct way of approaching this problem? Perhaps there is a straightforward solution, that doesn’t require installation of any CPAN modules? Thanks for your help.
#!perl
use strict;
use warnings;
use File::Basename;
#use Arrays::Utils;
opendir my $dir, "/data/test_all_runs" or die "Cannot open directory: $!";
my #run_folder = readdir $dir;
closedir $dir;
my $run_folder = pop #run_folder; print "The folder is".$run_folder."\n";
my $home="/data/";
my $CNV_file = $home."test_all_runs/".$run_folder."/CNV.txt";
my #CNVarray;
open(TXT2, "$CNV_file");
while (<TXT2>){
push (#CNVarray, $_);
}
close(TXT2);
foreach (#CNVarray){
chop($_);
}
my #array1 = map { $_->[1] } #CNVarray;
my #array2 = qw(MTOR JAK1 NRAS DDR2 MYCN ALK IDH1 ERBB4 RAF1 CTNNB1 PIK3CA DCUN1D1 FGFR3 PDGFRA KIT APC FGFR4 ROS1 ESR1 EGFR CDK6 MET SMO BRAF FGFR1 MYC JAK2 GNAQ RET FGFR2 HRAS CCND1 BIRC2 KRAS ERBB3 CDK4 AKT1 MAP2K1 IDH2 NF1 ERBB2 BRCA1 GNA11 MAP2K2 JAK3 AR MED12);
my %array1_hash;
my %array2_hash;
# Create a hash entry for each element in #array1
for my $element ( #array1 ) {
$array1_hash{$element} = #array1;
}
# Same for #array2: This time, use map instead of a loop
map { $array_2{$_} = 1 } #array2;
for my $entry ( #array2 ) {
if ( not $array1_hash{$entry} ) {
return 1; #Entry in #array2 but not #array1: Differ
}else {
return 0; #Arrays contain the same elements
}
#if ( keys %array_hash1 != keys %array_hash2 ) {
#return 1; #Arrays differ
}
Note The best version is reached at the end. It is a few lines of code.
If I get it right, you have a separate reference list of key-words that need to be in the second field in a row, with rows in that order. One way to find skipped rows is to iterate through both lists.
That approach can be picky and error prone but here it can be made easier by removing the front element from the reference list each time. Then you always need to compare the current line against the first element in the reference list. Here is the basic logic, with the better version further below.
use warnings;
use strict;
open my $cnv_fh, '<', $CNV_file or die "Can't open $CNV_file: $!";
my #CNVarray = <$cnv_fh>;
close $cnv_fh;
# chomp(#CNVarray);
my #ref_list = qw(MTOR JAK1 ...);
foreach my $line (#CNVarray)
{
if ( (split /\t/, $line)[1] eq $ref_list[0] ) { # good row
shift #ref_list;
print $line, "\n";
}
else {
shift #ref_list;
print "blank row found\n";
while ( (split /\t/, $line)[1] ne $ref_list[0] ) {
# multiple missing rows? keep going through the reference list
shift #ref_list;
print "blank row found\n";
}
}
# We are done with the array, but are there more reference items?
print "blank row found\n" for #ref_list;
The while loop is needed since multiple rows can be missing (in a row), so we need to get to the place in the reference list that does match the current row. A few notes on the code.
The filehandle read <...> in the list context returns a list with all lines from the resource.
The chop in the original code removes the last character, probably not what you want. It is the chomp that removes the new line (or really $/).
Tested against the reference list qw(AA BB CC DD EE) with the input file (note spaces not tabs)
1 AA first
2 BB more
5 EE last
To test with this, change /\t/ to /\s/ (what will then work for tabs as well). It prints
1 AA first
2 BB more
blank row found
blank row found
5 EE last
With further elements added to the #ref_list (FF etc) further blank ... lines are printed.
The code above can be simplified. Lines are also collected in an array, then printed to a new file.
use warnings;
use strict;
open my $cnv_fh, '<', $CNV_file or die "Can't open $CNV_file: $!";
my #CNVarray = <$cnv_fh>;
close $cnv_fh;
chomp(#CNVarray);
my #ref_list = qw(MTOR JAK1 ...);
my #new_lines;
foreach my $line (#CNVarray)
{
while ( (split /\t/, $line)[1] ne $ref_list[0] ) {
shift #ref_list;
push #new_lines, 'blank row found';
print "blank row found\n";
}
shift #ref_list;
push #new_lines, $line;
print $line, "\n";
}
# There may be more items remaining on the reference list
for (#ref_list) {
push #new_lines, 'blank row found';
print "blank row found\n"
}
my $filled_file = 'skipped_rows_added.txt';
open my $out_fh, '>', $filled_file or die "Can't open $filled_file: $!";
print $out_fh "$_\n" for #new_lines;
close $out_fh;
This behaves the same way with the test input above. It can be simplified further yet
foreach my $line (#CNVarray)
{
while ( (split /\t/, $line)[1] ne shift #ref_list ) {
print "blank row found\n";
}
print $line, "\n";
}
The shift returns the removed element, which is what need be tested against.
A note on split syntax, following the code update ("\t" changed to /\t/).
When invoked as split /$patt/, $str, the $patt is used as a regular expression, with a few very minor differences. So with /\s/ the string is split on white space as understood in regex, thus including the tab, for example.
With double quotes "..." used instead of /.../, what is inside is interpolated first which may result in surprises, in particular with escapes. (Unless it is used as m"..." in which case it is merely a regex with " being the delimiter.)
In the above code for the tab one can use /\t/, or "\t", or '\t' (or /\s/ which includes yet other types of space). The "\t" was changed to /\t/, which is better in my opinion, being clearer (it is a regex, no questions asked). Thanks to Borodin for the early edit and for the comment.
I would write this
The input file is read into a hash, keyed by the value of the second column. Then the hash is read back and printed in the specified sequence of keys
Most of the code is finding the input file and setting up the sequence of keys. The core of the program is only three lines of code
use strict;
use warnings 'all';
use File::Spec::Functions 'catfile';
my $home = '/data';
my #run_folder = grep -f, glob catfile($home, 'test_all_runs', '*', 'CNV.txt');
die "No CNV file found" unless #run_folder;
my $cnv_file = $run_folder[-1];
print "The file is $cnv_file\n\n";
my #sequence = qw/
MTOR JAK1 NRAS DDR2 MYCN ALK
IDH1 ERBB4 RAF1 CTNNB1 PIK3CA DCUN1D1
FGFR3 PDGFRA KIT APC FGFR4 ROS1
ESR1 EGFR CDK6 MET SMO BRAF
FGFR1 MYC JAK2 GNAQ RET FGFR2
HRAS CCND1 BIRC2 KRAS ERBB3 CDK4
AKT1 MAP2K1 IDH2 NF1 ERBB2 BRCA1
GNA11 MAP2K2 JAK3 AR MED12
/;
open my $fh, '<', $cnv_file or die qq{Unable to open "$cnv_file" for input: $!};
my %data;
$data{ (split)[1] } = $_ while <$fh>;
print $data{$_} // "no data for $_\n" for #sequence;
output
The file is /data/test_all_runs/XXX/CNV.txt
chr1:11174372 MTOR 42939 42939 7
chr1:65310459 JAK1 1948 1948 3
no data for NRAS
no data for DDR2
no data for MYCN
no data for ALK
no data for IDH1
no data for ERBB4
no data for RAF1
no data for CTNNB1
no data for PIK3CA
no data for DCUN1D1
no data for FGFR3
no data for PDGFRA
no data for KIT
no data for APC
no data for FGFR4
no data for ROS1
no data for ESR1
no data for EGFR
no data for CDK6
no data for MET
no data for SMO
no data for BRAF
no data for FGFR1
no data for MYC
no data for JAK2
no data for GNAQ
no data for RET
no data for FGFR2
no data for HRAS
no data for CCND1
no data for BIRC2
no data for KRAS
no data for ERBB3
no data for CDK4
no data for AKT1
no data for MAP2K1
no data for IDH2
no data for NF1
no data for ERBB2
no data for BRCA1
no data for GNA11
no data for MAP2K2
no data for JAK3
no data for AR
no data for MED12

Modifying CSV file and Preserving Order

The question that follows is a made up simplified example of a more complex problem that I'm trying to solve. I would like to preserve the structure of the code, especially the use of the %hash to store the outcomes for each patient but I do not need to read the data file into memory (but I cannot find a way of reading my csv data file line by line from the end.)
My sample data is made up of events that occur to patients. A patient can be added to the study (Event=B) or he can die (Event=D) or exit the study(Event=F.) Death and Exit are the only two possible outcomes for each patient.
For each event I have the date of occurrence (in hours from given point in time), the unique ID number of each patient, the event and the Outcome (a field set to 0 for every patient.)
I'm trying to write a code that will change the input file by putting next to each addition of a new patient, what is his eventual outcome (death or exit.)
In order to do so, I read the file from the end, and whenever I encounter a death or exit of a patient, I populate a hash that matches patient ID with outcome. When I encounter an event telling me that a new patient has been added to the study, I then match his ID with those in the hash and change the value of "Outcome" from 0 to either D or F.
I have been able to write a code that reads the file from bottom and then creates a new modified file with the updated value for Outcome. The problem is that since I read the input file from bottom to top and print each line after reading it, the output file is in reversed order and I do not know how to change this. Also, ideally I don't want to create a new file bu I would like to simply modify the input one. However, I have failed with every attempt to do so.
Sample data:
Data,PatientNumber,Event,Outcome
25201027,562962838335407,B,0
25201028,562962838335408,B,0
25201100,562962838335407,D,0
25201128,562962838335408,F,0
My code:
#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;
open (my $fh_input, "<", "mini_test2.csv")
or die "cannot open > mini_test2.csv: $!";
my #lines = <$fh_input>;
close $fh_input;
open (my $fh_output, ">>", "Revised_mini_test2.csv")
or die "cannot open > Revised_mini_test2.csv: $!";
my $length = scalar(#lines);
my %outcome;
my #input_variables;
for (my $i = 1; $i < #lines; $i++){
chomp($lines[$length-$i]);
#input_variables=split(/,/, $lines[$length - $i]);
if ($input_variables[2] eq "D" || $input_variables[2] eq "F"){
$outcome{$input_variables[1]} = $input_variables[2];
my $line = join(",", #input_variables);
print $fh_output $line . "\n";
}
elsif($input_variables[2] eq "B") {
$input_variables[3]=$outcome{$input_variables[1]};
my $line = join(",", #input_variables);
print $fh_output $line . "\n";
}
else{
# necessary since the actual data has many more possible "Events"
my $line = join(",", #input_variables);
print $fh_output $line . "\n";
}
}
close $fh_output;
EDIT: desired output should be
Data,PatientNumber,Event,Outcome
25201027,562962838335407,B,D
25201028,562962838335408,B,F
25201100,562962838335407,D,0
25201128,562962838335408,F,0
Also, an additional complication is that the unique patient ID after the exit of a patient gets re-used. This means that I cannot do a 1st pass and store the outcome for each patient and a 2nd one to update the values of Outcome.
EDIT 2: let me clarify that when I say that each patient has a "unique ID" I mean that there cannot be in the study, at the same time, two patients with the same ID. However, if a patient exits the study, his ID gets re-used.
Update
I have just read your additional information that patient numbers are re-used once they exit the study. Why you would design a system like that I don't know, but there it is
It becomes far harder to write something straightforward without reading the file into an array, so that's what I have done here
use strict;
use warnings;
use 5.010;
use autodie;
open my $fh, '<', 'mini_test2.csv';
my #data;
while ( <$fh> ) {
chomp;
push #data, [ split /,/ ];
}
my %outcome;
for ( my $i = $#data; $i > 0; --$i ) {
my ($patient_number, $event) = #{$data[$i]}[1,2];
if ( $event =~ /[DF]/ ) {
$outcome{$patient_number} = $event;
}
elsif ( $event =~ /[B]/ ) {
$data[$i][3] = delete $outcome{$patient_number} // 0;
}
}
print join(',', #$_), "\n" for #data;
output
Data,PatientNumber,Event,Outcome
25201027,562962838335407,B,D
25201028,562962838335408,B,F
25201100,562962838335407,D,0
25201128,562962838335408,F,0
There are a few ways to approach this. I have chosen to take two passes through the file, first accumulating the outcome for each patient in a hash, and then replacing all the outcome fields in the B records
use strict;
use warnings;
use 5.010;
use autodie;
use Fcntl ':seek';
my %outcome;
open my $fh, '<', 'mini_test2.csv';
<$fh>; # Drop header
while ( <$fh> ) {
chomp;
my #fields = split /,/;
my ($patient_number, $event) = #fields[1,2];
if ( $event =~ /[DF]/ ) {
$outcome{$patient_number} = $event;
}
}
seek $fh, 0, SEEK_SET; # Rewind
print scalar <$fh>; # Copy header
while ( <$fh> ) {
chomp;
my #fields = split /,/;
my ($patient_number, $event) = #fields[1,2];
if ( $event !~ /[DF]/ ) {
$fields[3] = $outcome{$patient_number} // 0;
}
print join(',', #fields), "\n";
}
output
Data,PatientNumber,Event,Outcome
25201027,562962838335407,B,D
25201028,562962838335408,B,F
25201100,562962838335407,D,0
25201128,562962838335408,F,0
What we can do is instead of printing out the line at each stage, we'll write it back to the array of lines. Then we can just print them out at the end.
for (my $i=$#lines; i>=0; i--)
{
chomp $lines[$i];
#input_variables = split /,/, $lines[$i];
if ($input_variables[2] eq "D" || $input_variables[2] eq "F")
{
$outcome{$input_variables[1]}=$input_variables[2];
}else
{
$input_variables[3]=$outcome{$input_variables[1]};
}
$line[$i] = join ",", #input_variables;
}
$, = "\n"; #Make list seperator for printing a newline.
print $fh_output #lines;
As for the second question of modifying the original file. It is possible to open a file for both reading and writing using modes "+<", "+>", or "+>>". Don't do this! It is error prone as you must replace data character by character.
The standard way to "modify" an existing file is to rename it, read from the renamed file, write to a new file with the original name, and delete the temp file.
my $file_name = "mini_test2.csv";
my $tmp_file_name = $file_name . ".tmp";
rename $file_name, $tmp_file_name;
open (my $fh_input, "<", $tmp_file_name)
or die "cannot open > $tmp_file_name: $!";
open (my $fh_output, ">>", $file_name)
or die "cannot open > $file_name: $!";
#Your code to process the data.
close $fh_input;
close $fh_output;
#delete the temp file
unlink $tmp_file_name;
But, in your case, you slurp all of the data into memory right away. Just open for writing that clobbers existing files
open (my $fh_output, ">", "mini_test2.csv")
or die "cannot open > mini_test2.csv: $!";

separate and outfile numeric values based on similarity of the values.

I think perl can do this, but I am pretty new to perl.
Hoping somebody can help me.
I have file like this (actual file is more than ten thousands lines, values are in ascending order, some values are duplicated).
1
2
2
35
45
I want to separate those lines into separate files based on the similarity of the values (for example difference of the value is less than 30).
outfile1
1
2
2
outfile2
35
45
Thanks
This is done very simply by just opening a new file every time it is necessary, i.e. for the first line of data and thereafter every time there is a gap of 30 or more.
This program expects the name of the input file as a parameter on the command line.
use strict;
use warnings;
use autodie;
my ($last, $fileno, $fh);
while (<>) {
my ($this) = /(\d+)/;
unless (defined $last and $this < $last + 30) {
open $fh, '>', 'outfile'.++$fileno;
}
print $fh $_;
$last = $this;
}
It should really be easy. Just remember the previous value in a variable so you can see whether the difference is large enough. You also have to count the output files created so far so you can name a new file when needed.
#!/usr/bin/perl
use warnings;
use strict;
my $threshold = 30;
my $previous;
my $count_out = 0;
my $OUTPUT;
while (<>) {
if (not defined $previous or $_ > $previous + $threshold) {
open $OUTPUT, '>', "outfile" . $count_out++ or die $!;
}
print $OUTPUT $_;
$previous = $_;
}

calculate average of small parts of column, grouped by key in perl?

This question is quite similar to this one How can I get the average and standard deviations grouped by key? but I don't manage to modify it to fit my problem.
I have a lot of files (.csv) with 7 columns, the last three columns look like this:
col5,col6,col7
1408,1,123
1408,2,234
1408,3,345
1408,4,456
1408,5,567
1408,6,678
1409,0,123
1409,1,234
1409,2,345
1409,3,456
1409,4,567
1409,5,678
1409,6,789
...
N,0,123
N,1,234
N,2,345
N,3,456
N,4,567
N,5,678
N,6,789
What I want to do is to calculate the average of the last column (col7) for all the values that have the same value in column 5 (col5), so 1408, 1409, 1410, ... until N and I don't know N. I want to print this average value next to the line (in col8) which contains a 3 in column 6 (col6). Do note that the value in column 6 (col6) goes from 0 to 6, but the first number of the file is not always 0. So what I want is:
col1,col2,col3,col4,col5,col6,col7,col8
bla,bla,bla,bla,1408,3,345,400.5
bla,bla,bla,bla,1409,3,456,456
...
bla,bla,bla,bla,N,3,456,456
I have some script I can use to calculate the average, but I have to be able to put my values into an array for that. Below is what I tried to do, but it doesn't work. Also, I'm just trying to learn Perl on my own, so if it looks like crap, I'm just trying!
open (FILE, "<", $dir.$file) or die;
my #lines = <FILE>;
foreach my $line(#lines) {
my ($col1,$col2,$col3,$col4,$col5,$col6,$col7) = split(/\,/, $line);
push #arrays5, $col5;
}
foreach my $array5(#arrays5) {
foreach my $line(#lines) {
my ($col1,$col2,$col3,$col4,$col5,$col6,$col7) = split(/\,/, $line);
if ($array5 == $col5) {
push #arrays7, $col7;
}
}
}
close(FILE);
One way using Text::CSV_XS module. It's not a built-in one, so it has to be installed from CPAN or similar tool.
Content of script.pl:
use warnings;
use strict;
use Text::CSV_XS;
my ($offset, $col_total, $row3, $rows_processed);
## Check arguments to the script.
die qq[Usage: perl $0 <input-file>\n] unless #ARGV == 1;
## Open input file.
open my $fh, q[<], shift or die qq[Open error: $!\n];
## Create the CSV object.
my $csv = Text::CSV_XS->new or
die qq[ERROR: ] . Text::CSV_XS->error_diag();
## Read file content seven lines each time.
while ( my $rows = $csv->getline_all( $fh, $offset, 7 ) ) {
## End when there is no more rows.
last unless #$rows;
## For each row in the group of seven...
for my $row ( 0 .. $#{$rows} ) {
## Get value of last column.
my $last_col_value = $rows->[ $row ][ $#{$rows->[$row]} ];
## If last column is not a number it is the header, so print it
## appending the eigth column and read next one.
unless ( $last_col_value =~ m/\A\d+\Z/ ) {
$csv->print( \*STDOUT, $rows->[ $row ] );
printf qq[,%s\n], q[col8];
next;
}
## Acumulate total amount for last column.
$col_total += $last_col_value;
## Get third row. The output will be this row with the
## average appended.
if ( $rows->[ $row ][-2] == 3 ) {
$row3 = [ #{ $rows->[ $row ] } ];
}
## Count processed rows.
++$rows_processed;
}
## Print row with its average.
if ( $rows_processed > 0 && ref $row3 ) {
$csv->print( \*STDOUT, $row3 );
printf qq[,%g\n], $col_total / $rows_processed;
}
## Initialize variables.
$col_total = $rows_processed = 0;
undef $row3;
}
Content of infile:
col1,col2,col3,col4,col5,col6,col7
bla,bla,bla,bla,1408,1,123
bla,bla,bla,bla,1408,2,234
bla,bla,bla,bla,1408,3,345
bla,bla,bla,bla,1408,4,456
bla,bla,bla,bla,1408,5,567
bla,bla,bla,bla,1408,6,678
bla,bla,bla,bla,1409,0,123
bla,bla,bla,bla,1409,1,234
bla,bla,bla,bla,1409,2,345
bla,bla,bla,bla,1409,3,456
bla,bla,bla,bla,1409,4,567
bla,bla,bla,bla,1409,5,678
bla,bla,bla,bla,1409,6,789
Run it like:
perl script.pl infile
With following output:
col1,col2,col3,col4,col5,col6,col7,col8
bla,bla,bla,bla,1408,3,345,400.5
bla,bla,bla,bla,1409,3,456,456
Before we try to complete the answer, would you try this and tell me how close it comes to what you want?
#!/usr/bin/perl
use warnings;
use strict;
my $target = 3;
my %summary;
while(<>) {
chomp;
my ($col1,$col2,$col3,$col4,$col5,$col6,$col7) = split /\,/;
$summary{$col5}{total} += $col7;
++$summary{$col5}{count};
$summary{$col5}{line} = $_ if $col6 == $target;
}
$summary{$_}{average} = $summary{$_}{total} / $summary{$_}{count}
for keys %summary;
print "${summary{$_}{line}},${summary{$_}{average}}\n"
for sort keys %summary;
If close enough, then you may wish to finish on your own. If not, then we can discuss the matter further.
Note that you can replace the <> with <FILE> if you prefer to read from your data file rather than from standard input.
IMPLEMENTATION NOTES
The code relies on Perl's autovivification feature. Observe for instance the line ++$summary{$col5}{count};, which seems initially to increment a nonexistent counter. However, this is actually standard Perl idiom. If you try to do something arithmetical (like incrementation) to an object that does not exist, Perl implicitly creates the object, initializes it to zero, and then does the thing you wanted (like incrementation) to it.
It would probably be unwise for a more sober programming language like C++ to autovivify, but years of experience suggest that autovivification strikes the right balance between order and convenience in a slightly less sober language like Perl.
On a more elementary level, the code will probably make sense only to those used to Perl's hashes. However, if you've not used Perl's hashes before, this would be as good a chance as any to learn them. The hash is a central pillar of the language, and the above makes a fairly typical example of its use.
In this case, we have a hash of hashes, which again is fairly typical.
This should do the trick. Replace Cols[index] appropriately.
use Data::Dumper ;
open (FILE, "<", '/tmp/myfile') or die;
my #lines ;
my (%Sum,%Count);
chomp(#lines = <FILE>);
foreach my $line(#lines) {
next if $line =~ /col/;
my #Cols = split /,/, $line;
$Sum{$Cols[0]} += $Cols[2] ;
$Count{$Cols[0]}++;
}
foreach my $line(#lines) {
if($line=~/col/) {
print "$line,colX\n" ;
next;
}
my #Cols = split /,/, $line;
if($Cols[1]==3) {
print "$line,",$Sum{$Cols[0]}/$Count{$Cols[0]},"\n" ;
} else {
print "$line,-1\n";
}
}
Sample input /tmp/myfile
col5,col6,col7
1408,1,123
1408,2,234
1408,3,345
1408,4,456
1408,5,567
1408,6,678
1409,0,123
1409,1,234
Sample output
col5,col6,col7,colX
1408,1,123,-1
1408,2,234,-1
1408,3,345,400.5
1408,4,456,-1
1408,5,567,-1
1408,6,678,-1
1409,0,123,-1
1409,1,234,-1

Perl merging 2 csv files line by line with a primary key

Edit: solution added.
Hi, I currently have some working albeit slow code.
It merges 2 CSV files line by line using a primary key.
For example, if file 1 has the line:
"one,two,,four,42"
and file 2 has this line;
"one,,three,,42"
where in 0 indexed $position = 4 has the primary key = 42;
then the sub: merge_file($file1,$file2,$outputfile,$position);
will output a file with the line:
"one,two,three,four,42";
Every primary key is unique in each file, and a key might exist in one file but not in the other (and vice versa)
There are about 1 million lines in each file.
Going through every line in the first file, I am using a hash to store the primary key, and storing the line number as the value. The line number corresponds to an array[line num] which stores every line in the first file.
Then I go through every line in the second file, and check if the primary key is in the hash, and if it is, get the line from the file1array and then add the columns I need from the first array to the second array, and then concat. to the end. Then delete the hash, and then at the very end, dump the entire thing to file. (I am using a SSD so I want to minimise file writes.)
It is probably best explained with a code:
sub merge_file2{
my ($file1,$file2,$out,$position) = ($_[0],$_[1],$_[2],$_[3]);
print "merging: \n$file1 and \n$file2, to: \n$out\n";
my $OUTSTRING = undef;
my %line_for;
my #file1array;
open FILE1, "<$file1";
print "$file1 opened\n";
while (<FILE1>){
chomp;
$line_for{read_csv_string($_,$position)}=$.; #reads csv line at current position (of key)
$file1array[$.] = $_; #store line in file1array.
}
close FILE1;
print "$file2 opened - merging..\n";
open FILE2, "<", $file2;
my #from1to2 = qw( 2 4 8 17 18 19); #which columns from file 1 to be added into cols. of file 2.
while (<FILE2>){
print "$.\n" if ($.%1000) == 0;
chomp;
my #array1 = ();
my #array2 = ();
my #array2 = split /,/, $_; #split 2nd csv line by commas
my #array1 = split /,/, $file1array[$line_for{$array2[$position]}];
# ^ ^ ^
# prev line lookup line in 1st file,lookup hash, pos of key
#my #output = &merge_string(\#array1,\#array2); #merge 2 csv strings (old fn.)
foreach(#from1to2){
$array2[$_] = $array1[$_];
}
my $outstring = join ",", #array2;
$OUTSTRING.=$outstring."\n";
delete $line_for{$array2[$position]};
}
close FILE2;
print "adding rest of lines\n";
foreach my $key (sort { $a <=> $b } keys %line_for){
$OUTSTRING.= $file1array[$line_for{$key}]."\n";
}
print "writing file $out\n\n\n";
write_line($out,$OUTSTRING);
}
The first while is fine, takes less than 1 minute, however the second while loop takes about 1 hour to run, and I am wondering if I have taken the right approach. I think it is possible for a lot of speedup? :) Thanks in advance.
Solution:
sub merge_file3{
my ($file1,$file2,$out,$position,$hsize) = ($_[0],$_[1],$_[2],$_[3],$_[4]);
print "merging: \n$file1 and \n$file2, to: \n$out\n";
my $OUTSTRING = undef;
my $header;
my (#file1,#file2);
open FILE1, "<$file1" or die;
while (<FILE1>){
if ($.==1){
$header = $_;
next;
}
print "$.\n" if ($.%100000) == 0;
chomp;
push #file1, [split ',', $_];
}
close FILE1;
open FILE2, "<$file2" or die;
while (<FILE2>){
next if $.==1;
print "$.\n" if ($.%100000) == 0;
chomp;
push #file2, [split ',', $_];
}
close FILE2;
print "sorting files\n";
my #sortedf1 = sort {$a->[$position] <=> $b->[$position]} #file1;
my #sortedf2 = sort {$a->[$position] <=> $b->[$position]} #file2;
print "sorted\n";
#file1 = undef;
#file2 = undef;
#foreach my $line (#file1){print "\t [ #$line ],\n"; }
my ($i,$j) = (0,0);
while ($i < $#sortedf1 and $j < $#sortedf2){
my $key1 = $sortedf1[$i][$position];
my $key2 = $sortedf2[$j][$position];
if ($key1 eq $key2){
foreach(0..$hsize){ #header size.
$sortedf2[$j][$_] = $sortedf1[$i][$_] if $sortedf1[$i][$_] ne undef;
}
$i++;
$j++;
}
elsif ( $key1 < $key2){
push(#sortedf2,[#{$sortedf1[$i]}]);
$i++;
}
elsif ( $key1 > $key2){
$j++;
}
}
#foreach my $line (#sortedf2){print "\t [ #$line ],\n"; }
print "outputting to file\n";
open OUT, ">$out";
print OUT $header;
foreach(#sortedf2){
print OUT (join ",", #{$_})."\n";
}
close OUT;
}
Thanks everyone, the solution is posted above. It now takes about 1 minute to merge the whole thing! :)
Two techniques come to mind.
Read the data from the CSV files into two tables in a DBMS (SQLite would work just fine), and then use the DB to do a join and write the data back out to CSV. The database will use indexes to optimize the join.
First, sort each file by primary key (using perl or unix sort), then do a linear scan over each file in parallel (read a record from each file; if the keys are equal then output a joined row and advance both files; if the keys are unequal then advance the file with the lesser key and try again). This step is O(n + m) time instead of O(n * m), and O(1) memory.
What's killing the performance is this code, which is concatenating millions of times.
$OUTSTRING.=$outstring."\n";
....
foreach my $key (sort { $a <=> $b } keys %line_for){
$OUTSTRING.= $file1array[$line_for{$key}]."\n";
}
If you want to write to the output file only once, accumulate your results in an array, and then print them at the very end, using join. Or, even better perhaps, include the newlines in the results and write the array directly.
To see how concatenation does not scale when crunching big data, experiment with this demo script. When you run it in concat mode, things start slowing down considerably after a couple hundred thousand concatenations -- I gave up and killed the script. By contrast, simply printing an array of a million lines took less than a than a minute on my machine.
# Usage: perl demo.pl 50 999999 concat|join|direct
use strict;
use warnings;
my ($line_len, $n_lines, $method) = #ARGV;
my #data = map { '_' x $line_len . "\n" } 1 .. $n_lines;
open my $fh, '>', 'output.txt' or die $!;
if ($method eq 'concat'){ # Dog slow. Gets slower as #data gets big.
my $outstring;
for my $i (0 .. $#data){
print STDERR $i, "\n" if $i % 1000 == 0;
$outstring .= $data[$i];
}
print $fh $outstring;
}
elsif ($method eq 'join'){ # Fast
print $fh join('', #data);
}
else { # Fast
print $fh #data;
}
If you want merge you should really merge. First of all you have to sort your data by key and than merge! You will beat even MySQL in performance. I have a lot of experience with it.
You can write something along those lines:
#!/usr/bin/env perl
use strict;
use warnings;
use Text::CSV_XS;
use autodie;
use constant KEYPOS => 4;
die "Insufficient number of parameters" if #ARGV < 2;
my $csv = Text::CSV_XS->new( { eol => $/ } );
my $sortpos = KEYPOS + 1;
open my $file1, "sort -n -k$sortpos -t, $ARGV[0] |";
open my $file2, "sort -n -k$sortpos -t, $ARGV[1] |";
my $row1 = $csv->getline($file1);
my $row2 = $csv->getline($file2);
while ( $row1 and $row2 ) {
my $row;
if ( $row1->[KEYPOS] == $row2->[KEYPOS] ) { # merge rows
$row = [ map { $row1->[$_] || $row2->[$_] } 0 .. $#$row1 ];
$row1 = $csv->getline($file1);
$row2 = $csv->getline($file2);
}
elsif ( $row1->[KEYPOS] < $row2->[KEYPOS] ) {
$row = $row1;
$row1 = $csv->getline($file1);
}
else {
$row = $row2;
$row2 = $csv->getline($file2);
}
$csv->print( *STDOUT, $row );
}
# flush possible tail
while ( $row1 ) {
$csv->print( *STDOUT, $row1 );
$row1 = $csv->getline($file1);
}
while ( $row2 ) {
$csv->print( *STDOUT, $row2 );
$row2 = $csv->getline($file1);
}
close $file1;
close $file2;
Redirect output to file and measure.
If you like more sanity around sort arguments you can replace file opening part with
(open my $file1, '-|') || exec('sort', '-n', "-k$sortpos", '-t,', $ARGV[0]);
(open my $file2, '-|') || exec('sort', '-n', "-k$sortpos", '-t,', $ARGV[1]);
I can't see anything that strikes me as obviously slow, but I would make these changes:
First, I'd eliminate the #file1array variable. You don't need it; just store the line itself in the hash:
while (<FILE1>){
chomp;
$line_for{read_csv_string($_,$position)}=$_;
}
Secondly, although this shouldn't really make much of a difference with perl, I wouldn't add to $OUTSTRING all the time. Instead, keep an array of output lines and push onto it each time. If for some reason you still need to call write_line with a massive string you can always use join('', #OUTLINES) at the end.
If write_line doesn't use syswrite or something low-level like that, but rather uses print or other stdio-based calls, then you aren't saving any disk writes by building up the output file in memory. Therefore, you might as well not build your output up in memory at all, and instead just write it out as you create it. Of course if you are using syswrite, forget this.
Since nothing is obviously slow, try throwing Devel::SmallProf at your code. I've found that to be the best perl profiler for producing those "Oh! That's the slow line!" insights.
Assuming around 20 bytes lines each of your file would amount to about 20 MB, which isn't too big.
Since you are using hash your time complexity doesn't seem to be a problem.
In your second loop, you are printing to the console for each line, this bit is slow. Try removing that should help a lot.
You can also avoid the delete in the second loop.
Reading multiple lines at a time should also help. But not too much I think, there is always going to be a read ahead behind the scenes.
I'd store each record in a hash whose keys are the primary keys. A given primary key's value is a reference to an array of CSV values, where undef represents an unknown value.
use 5.10.0; # for // ("defined-or")
use Carp;
use Text::CSV;
sub merge_csv {
my($path,$record) = #_;
open my $fh, "<", $path or croak "$0: open $path: $!";
my $csv = Text::CSV->new;
local $_;
while (<$fh>) {
if ($csv->parse($_)) {
my #f = map length($_) ? $_ : undef, $csv->fields;
next unless #f >= 1;
my $primary = pop #f;
if ($record->{$primary}) {
$record->{$primary}[$_] //= $f[$_]
for 0 .. $#{ $record->{$primary} };
}
else {
$record->{$primary} = \#f;
}
}
else {
warn "$0: $path:$.: parse failed; skipping...\n";
next;
}
}
}
Your main program will resemble
my %rec;
merge_csv $_, \%rec for qw/ file1 file2 /;
The Data::Dumper module shows that the resulting hash given the simple inputs from your question is
$VAR1 = {
'42' => [
'one',
'two',
'three',
'four'
]
};