I need a way to take the numbers in one line in my .csv file and multiply them together, and then add the products from each line together to get just one number. My .csv file looks something like:
1,1
2,3
3,4
I know the answer should be 19, but I'm not sure how exactly to program it in Perl. I have both numbers split into different variables by:
($x,$y) = split (/,/, $line)
I've already read the file in and all that, I just need help with this one part of my code.
If anyone could point me in the right direction I would really appreciate it.
A naive solution could look like this:
use strict;
use warnings FATAL => 'all';
my $total;
open(my $fh, '<', "temp.csv");
while( my $line = <$fh> ) {
my ($x, $y) = split(',', $line);
$total += ($x * $y);
}
print "Total is: $total\n";
In short form
perl -F, -anE'$s+=$F[0]*$F[1]}{say$s'
my $sum = 0;
open my $csv, '<', $filename or die $!;
while(my $line = <$csv>) {
my $prod = 1;
$prod *= $_ for split ',', $line;
$sum += $prod;
}
Related
I am trying to parse data like:
header1
-------
var1 0
var2 5
var3 9
var6 1
header2
-------
var1 -3
var3 5
var5 0
Now I want to get e.g. var3 for header2. Whats the best way to do this?
So far I was parsing my files line-by-line via
open(FILE,"< $file");
while (my $line = <FILE>){
# do stuff
}
but I guess it's not possible to handle multiline parsing properly.
Now I am thinking to parse the file at once but wasn't successful so far...
my #Input;
open(FILE,"< $file");
while (<FILE>){ #Input = <FILE>; }
if (#Input =~ /header2/){
#...
}
The easier way to handle this is "paragraph mode".
local $/ = "";
while (<>) {
my ($header, $body) =~ /^([^\n]*)\n-+\n(.*)/s
or die("Bad data");
my #data = map [ split ], split /\n/, $body;
# ... Do something with $header and #data ...
}
The same can be achieved without messing with $/ as follows:
my #buf;
while (1) {
my $line = <>;
$line =~ s/\s+\z// if !defined($line);
if (!length($line)) {
if (#buf) {
my $header = shift(#buf);
shift(#buf);
my #data = map [ split ], splice(#buf);
# ... Do something with $header and #data ...
}
last if !defined($line);
next;
}
push #buf, $line;
}
(In fact, the second snippet includes a couple of small improvements over the first.)
Quick comments on your attempt:
The while loop is useless because #Input = <FILE> places the remaining lines of the file in #Input.
#Input =~ /header2/ matches header2 against the stringification of the array, which is the stringification of the number of elements in #Input. If you want to check of an element of #Input contains header2, will you will need to loop over the elements of #Inputs and check them individually.
while (<FILE>){ #Input = <FILE>; }
This doesn't make much sense. "While you can read a record from FILE, read all of the data on FILE into #Input". I think what you actually want is just:
my #Input = <FILE>;
if (#Input =~ /header2/){
This is quite strange too. The binding operator (=~) expects scalar operands, so it evaluates both operands in scalar context. That means #Input will be evaluated as the number of elements in #Input. That's an integer and will never match "header2".
A couple of approaches. Firstly a regex approach.
#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
my $file = 'file';
open my $fh, '<', $file or die $!;
my $data = join '', <$fh>;
if ($data =~ /header2.+var3 (.+?)\n/s) {
say $1;
} else {
say 'Not found';
}
The key to this is the /s on the m// operator. Without it, the two dots in the regex won't match newlines.
The other approach is more of a line by line parser.
#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
my $file = 'file';
open my $fh, '<', $file or die $!;
my $section = '';
while (<$fh>) {
chomp;
# if the line all word characters,
# then we've got a section header.
if ($_ !~ /\W/) {
$section = $_;
next;
}
my ($key, $val) = split;
if ($section eq 'header2' and $key eq 'var3') {
say $val;
last;
}
}
We read the file a line at a time and make a note of the section headers. For data lines, we split on whitespace and check to see if we're in the right section and have the right key.
In both cases, I've switched to using a more standard approach (lexical filehandles, 3-arg open(), or die $!) for opening the file.
What this program is meant to do is that it reads a text file which looks like:
Item \t\t Price
apple \t\t 20
orange \t\t 50
lime \t\t 30
I'm using split function to split these 2 columns and then i should apply a -25% discount on all items and print it out to a new file. My code so far does what i want but the new text file has a '0' value under my last number in price column. I also get 2 errors if i run it with "use warnings" which are:
Use of uninitialized value $item in multiplication * ...
Use of uninitialized value $item[0] in concatenation (.) ...
I should also tell total number of items calculated but i get like 5 1's instead of 5. (11111 instead of 5)
use strict;
use warnings;
my $filename = 'shop.txt';
if (-e $filename){
open (IN, $filename);
}
else{
die "Can't open input file for reading: $!";
}
open (OUT,">","discount.txt") or die "Can't open output file for writing: $!";
my $header = <IN>;
print OUT $header;
while (<IN>) {
chomp;
my #items = split(/\t\t/);
foreach my $item ($items[1]){
my $discount = $item * (0.75);
print OUT "$items[0]\t\t$discount\n";
}
}
This is too complicated and not clear what are you doing in foreach loop and you are not skipping empty lines. Keep it simple:
use warnings;
use strict;
use v5.10;
<>; # skip header
while(my $line = <>)
{
chomp $line;
next unless ($line);
my ($title, $price ) = split /\s+/, $line;
if( $title && defined $price )
{
$price *= 0.75;
say "$title\t\t$price";
}
}
and run like
perl script.pl <input.txt >output.txt
use strict;
use warnings;
my $filename = 'shop.txt';
if (-e $filename){
open (IN, $filename);
}
else{
die "Can't open input file for reading: $!";
}
open (OUT,">","discount.txt") or die "Can't open output file for writing: $!";
my $header = <IN>;
my $item;
my $price;
print OUT $header;
while (<IN>) {
chomp;
($item, $price) = split(/\t\t/);
my $discount = $price*0.75;
print OUT "$item $discount\n";
}
This should help! :)
If the total item count isn't very important to you:
$ perl -wane '$F[1] *= 0.75 if $. > 1; print join("\t", #F), "\n";' input.txt
Output:
Item Price
apple 15
orange 37.5
lime 22.5
If you really need the total item count:
$ perl -we 'while (<>) { #F = split; if ($. > 1) { $F[1] *= 0.75; $i++ } print join("\t", #F), "\n"; } print "$i items\n";' input.txt
Output:
Item Price
apple 15
orange 37.5
lime 22.5
3 items
I'd use this approach
#!/usr/bin/perl
use strict;
use warnings;
my %items;
my $filename = 'shop.txt';
my $discount = 'discount.txt';
open my $in, '<', $filename or die "Failed to open file! : $!\n";
open my $out, ">", $discount or die "Can't open output file for writing: $!";
print $out "Item\t\tPrice\n";
my $cnt = 0;
while (my $line = <$in>) {
chomp $line;
if (my ($item,$price) = $line =~ /(\w.+)\s+([0-9.]+)/){
$price = $price * (0.75);
print $out "$item\t\t$price\n";
$items{$item} = $price;
$cnt++;
}
}
close($in);
close($out);
my $total = keys %items;
print "Total items - $total \n";
print "Total items - $cnt\n";
Using regex capture groups to capture the item and price (using \w.+ in case the item is 2 words like apple sauce), this will also prevent empty lines from printing to file.
I also hard coded the Item and Price header, probably a good idea if you are going to be using a consistent header.
Hope it helps
---Update ----
I added 2 examples of a total count in my script. The first one is using a hash and printing out the hash size, the second method is using a counter. The hash option is good except if your list has 2 items that are the same in which case the key of the hash will be overridden with the last item found which shares the same name. The counter is a simple solution.
This question already has answers here:
Counting number of occurrences of a string inside another (Perl)
(4 answers)
Closed 7 years ago.
I have to check how many times was "," in each line in file. Anybody have idea how can I do it in Perl?
On this moment my code looks like it:
open($list, "<", $student_list)
while ($linelist = <$list>)
{
printf("$linelist");
}
close($list)
But I have no idea how to check how many times is "," in each $linelist :/
Use the transliteration operator in counting mode:
my $commas = $linelist =~ y/,//;
Edited in your code :
use warnings;
use strict;
open my $list, "<", "file.csv" or die $!;
while (my $linelist = <$list>)
{
my $commas = $linelist =~ y/,//;
print "$commas\n";
}
close($list);
If you just want to count the number of somethings in a file, you don't need to read it into memory. Since you aren't changing the file, mmap would be just fine:
use File::Map qw(map_file);
map_file my $map, $filename, '<';
my $count = $map =~ tr/,//;
#! perl
# perl script.pl [file path]
use strict;
use warnings;
my $file = shift or die "No file name provided";
open(my $IN, "<", $file) or die "Couldn't open file $file: $!";
my #matches = ();
my $index = 0;
# while <$IN> will get the file one line at a time rather than loading it all into memory
while(<$IN>){
my $line = $_;
my $current_count = 0;
# match globally, meaning keep track of where the last match was
$current_count++ while($line =~ m/,/g);
$matches[$index] = $current_count;
$index++;
}
$index = 0;
for(#matches){
$index++;
print "line $index had $_ matches\n"
}
You can use mmap Perl IO layer instead of File::Map. It is almost as efficient as former but most probably present in your Perl installation without needing installing a module. Next, using y/// is more efficient than m//g in array context.
use strict;
use warnings;
use autodie;
use constant STUDENT_LIST => 'text.txt';
open my $list, '<:mmap', STUDENT_LIST;
while ( my $line = <$list> ) {
my $count = $line =~ y/,//;
print "There is $count commas at $.. line.\n";
}
If you would like grammatically correct output you can use Lingua::EN::Inflect in the right place
use Lingua::EN::Inflect qw(inflect);
print inflect "There PL_V(is,$count) $count PL_N(comma,$count) at ORD($.) line.\n";
Example output:
There are 7 commas at 1st line.
There are 0 commas at 2nd line.
There is 1 comma at 3rd line.
There are 2 commas at 4th line.
There are 7 commas at 5th line.
Do you want #commas for each line in the file, or #commas in the entire file?
On a per-line basis, replace your while loop with:
my #data = <list>;
foreach my $line {
my #chars = split //, $line;
my $count = 0;
foreach my $c (#chars) { $count++ if $c eq "," }
print "There were $c commas\n";
}
I am extremely new to the Perl process. I am very much enjoying the learning curve and Perl but I am frustrated beyond belief and have spent many, many hours on one task achieving little to no results.
#!/usr/bin/perl
use strict;
print "Average value of retroviruses for the length of each genome and each of the genes:\n"; #create a title for the script
my $infile = "Lab1_table.txt"; # This is the file path.
open INFILE, $infile or die "Can't open $infile: $!"; # Provides an error message if the file can'tbe found.
# set my initial values.
my $tally = 0;
my #header = ();
my #averages = ();
# create my first loop to run through the file by line.
while (my $line = <INFILE>){
chomp $line;
print "$line\n";
# add one to the loop and essentially remove the header line of value.
# the first line is what was preventing me from caclulating averages as Perl can't calculate words.
my #row = split /\t/, $line; # split the file by tab characters.
$tally++; #adds one to the tally.
if ( $tally == 1 ) { #if the tally = 1 the row is determined as a the header.
#header = #row;
}
# if the tally is anything else besides 1 then it will read those rows.
else {
for( my $i = 1; $i < scalar #row; $i++ ) {
$averages[$i] += $row[$i];
}
foreach my $element (#row){
}
foreach my $i (0..4){
$averages[$i] = $averages[$i] + $row[1..4];
}
}
}
print "Average values of genome, gag, pol and env:\n";
for( my $i = 1; $i < scalar #averages; $i++ ) { # this line is used to determine the averages of the columns and print the values
print $averages[$i]/($tally-1), "\n";
}
SO, I got the results to come up with what I wanted (not in the exact format I wanted but as close as I can seem to get at the moment) and they do average the columns.
The issue now is writing to a an outfile. I am trying to get my table and results from the previous code to appear in my outfile. I get a good file name but no results.
foreach my $i (1){
my $outfile= "Average_values".".txt";
open OUTFILE, ">$outfile" or die "$outfile: $!";
print "Average values of genome, gag, pol and env:\n";
}
close OUTFILE;
close INFILE;
I feel like there is an easy way to do this and a hard way and I have taken the very hard way. Any help would be much appreciated.
You did not tell Perl where to print:
print OUTFILE "Average values of genome, gag, pol and env:\n";
BTW, together with use strict, also use warnings. And for working with files, use lexical filehandles and the three argument form of open:
open my $FH, '>', $filename or die $!;
print $FH 'Something';
close $FH or die $!;
I'm new to Perl and I'm afraid I am stuck and wanted to ask if someone might be able to help me.
I have a file with two columns (tab separated) of oldname and newname.
I would like to use the oldname as key and newname as value and store it as a hash.
Then I would like to open a different file (gff file) and replace all the oldnames in there with the newnames and write it to another file.
I have given it my best try but am getting a lot of errors.
If you could let me know what I am doing wrong, I would greatly appreciate it.
Here are how the two files look:
oldname newname(SFXXXX) file:
genemark-scaffold00013-abinit-gene-0.18 SF130001
augustus-scaffold00013-abinit-gene-1.24 SF130002
genemark-scaffold00013-abinit-gene-1.65 SF130003
file to search and replace in (an example of one of the lines):
scaffold00013 maker gene 258253 258759 . - . ID=maker-scaffold00013-augustus-gene-2.187;Name=maker-scaffold00013-augustus-gene-2.187;
Here is my attempt:
#!/usr/local/bin/perl
use warnings;
use strict;
my $hashfile = $ARGV[0];
my $gfffile = $ARGV[1];
my %names;
my $oldname;
my $newname;
if (!defined $hashfile) {
die "Usage: $0 hash_file gff_file\n";
}
if (!defined $gfffile) {
die "Usage: $0 hash_file gff_file\n";
}
###save hashfile with two columns, oldname and newname, into a hash with oldname as key and newname as value.
open(HFILE, $hashfile) or die "Cannot open $hashfile\n";
while (my $line = <HFILE>) {
chomp($line);
my ($oldname, $newname) = split /\t/;
$names{$oldname} = $newname;
}
close HFILE;
###open gff file and replace all oldnames with newnames from %names.
open(GFILE, $gfffile) or die "Cannot open $gfffile\n";
while (my $line2 = <GFILE>) {
chomp($line2);
eval "$line2 =~ s/$oldname/$names{oldname}/g";
open(OUT, ">SFrenamed.gff") or die "Cannot open SFrenamed.gff: $!";
print OUT "$line2\n";
close OUT;
}
close GFILE;
Thank you!
Your main problem is that you aren't splitting the $line variable. split /\t/ splits $_ by default, and you haven't put anything in there.
This program builds the hash, and then constructs a regex from all the keys by sorting them in descending order of length and joining them with the | regex alternation operator. The sorting is necessary so that the longest of all possible choices is selected if there are any alternatives.
Every occurrence of the regex is replaced by the corresponding new name in each line of the input file, and the output written to the new file.
use strict;
use warnings;
die "Usage: $0 hash_file gff_file\n" if #ARGV < 2;
my ($hashfile, $gfffile) = #ARGV;
open(my $hfile, '<', $hashfile) or die "Cannot open $hashfile: $!";
my %names;
while (my $line = <$hfile>) {
chomp($line);
my ($oldname, $newname) = split /\t/, $line;
$names{$oldname} = $newname;
}
close $hfile;
my $regex = join '|', sort { length $b <=> length $a } keys %names;
$regex = qr/$regex/;
open(my $gfile, '<', $gfffile) or die "Cannot open $gfffile: $!";
open(my $out, '>', 'SFrenamed.gff') or die "Cannot open SFrenamed.gff: $!";
while (my $line = <$gfile>) {
chomp($line);
$line =~ s/($regex)/$names{$1}/g;
print $out $line, "\n";
}
close $out;
close $gfile;
Why are you using an eval? And $oldname is going to be undefined in the second while loop, because the first while loop you redeclare them in that scope (even if you used the outer scope, it would store the very last value that you processed, which wouldn't be helpful).
Take out the my $oldname and my $newname at the top of your script, it is useless.
Take out the entire eval line. You need to repeat the regex for each thing you want to replace. Try something like:
$line2 =~ s/$_/$names{$_}/g for keys %names;
Also see Borodin's answer. He made one big regex instead of a loop, and caught your lack of the second argument to split.