I am new to this field. So kindly go easy on me. I have two arrays:
#array1 = ("ABC321", "CDB672", "PLE89",....);
#array2 = ("PLE89", "ABC678", "LMD789",...);
I want to compare elements of these two different arrays. But, I want to only match letters with letters. So for instance, if arrays are compared, $array[2] element (PLE) should match with $array2[0] (PLE) and similarly $array1[0] (ABC) should match with $array[1] (ABC). I am able to do it one at time but not able to compare all elements of both array at the same time (that is looping the arrays).
my ($value1)= ($array[2]=~ /([A-Z]+)[0-9]+/);
print "Value1: $value1 \n";
my ($value2)= ($array[0]=~ /([A-Z]+)[0-9]+/);
print "Value2 : $value2 \n";
if ($value1 eq $value2){
print " length \n";
}
Any suggestions on how to do I set up loop for both arrays at the same time?
You can use a hash as a lookup device and get an O(m+n) solution (where m is the length of array1 and n is the length of array2).
#!/usr/bin/perl
use strict;
use warnings;
my #array1 = qw(ABC321 CDB672 PLE89);
my #array2 = qw(PLE89 ABC678 LMD789);
my %seen;
for my $item (#array1) {
die "not a valid item: $item"
unless my ($key) = $item =~ /([A-Z]+)/;
#we are using an array to hold the items in case
#the same key shows up more than once in an array
#this code can be simpler if you can guarantee
#that the keys are unique
push #{$seen{$key}}, $item;
}
for my $item (#array2) {
die "not a valid item: $item"
unless my ($key) = $item =~ /([A-Z]+)/;
if (exists $seen{$key}) {
print "$item is in array1, it matches #{$seen{$key}}\n";
} else {
print "$item is not in array1\n";
}
}
Language-agnostic suggestion would be to sort both arrays first (should take you O(n lg(n)), then compare with two iterators in linear time.
If performance is not an issue, just keep it simple and go with quadratic number of pair-wise comparisons.
While sorting you can also get rid of digits in the end.
Related
I'm having trouble understanding why this code will not output anything:
#!/usr/bin/perl -w
use strict;
my %allwords = (); #Create an empty hash list.
my $running_total = 0;
while (<>) {
print "In the loop 1";
chomp;
print "Got here";
my #words = split(/\W+/,$_);
}
foreach my $val (my #words) {
print "$val\n";
}
And I run it from the terminal using the command:
perl wordfinder.pl < exampletext.txt
I would expect the code above to output each word from the input file, but it does not output anything other than "In the loop 1" and "Got here". I'm trying to separate the input file word by word, using the split parameter I specified.
Update 1: Here, I have declared the variables within their proper scope, which was my main issue. Now I am getting all of the words from the input file to output on the terminal:
my %allwords = (); #Create an empty hash list.
my $running_total = 0;
my #words = ();
my $val;
while (<>) {
print "Inputting words into an array! \n";
chomp;
#words = split(/\W+/,$_);
}
print("Words have been input successfully, performing analysis: \n");
foreach $val (#words) {
print "$val\n";
}
UPDATE 2: Progress has been made. Now, we put all words from any input files into a hash, and then print each unique key (i.e. each unique word found across all input files) from the hash.
#!/usr/bin/perl -w
use strict;
# Description: We want to take ALL text files from the command line input and calculate
# the frequencies of the words contained therein.
# Step 1: Loop over all words in all input files, and put each new unique word in a
# hash (check to see if contained in hash, if not, put the word in; if the word already
# exists in the hash, then increase its "total" by 1). Also, keep a running total of
# all words.
print("Welcome to word frequency finder. \n");
my $running_total = 0;
my %words;
my $val;
while (<>) {
chomp;
foreach my $str (split(/\W+/,$_)) {
$words{$str}++;
$running_total++;
}
}
print("Words have been input successfully, performing analysis: \n");
# Step 2: Loop over all entries in the hash and look for the word (key) with the
# maximum amount, and then remove this from the hash and put in a separate list.
# Do this until the size of the separate list is 10, since we want the top 10 words.
foreach $val (keys %words) {
print "$val\n";
}
Since you've already completed step 1, you're left with getting your top ten most common words. Rather than looping through the hash and finding the most frequent entry, let's let Perl do the work for us by sorting the hash by its values.
To sort the %words hash by its keys, we can use the expression sort keys %words; to sort a hash by its values, but be able to access its keys, we need a more complex expression:
sort { $words{$a} <=> $words{$a} } keys %words
Breaking it down, to sort numerically, we use the expression
sort { $a <=> $b } #array
(see [perl sort][1] for more on the special variables $a and $b used in sorting)
sort { $a <=> $b } keys %words
would sort on the hash keys, so to sort on the values, we do
sort { $words{$a} <=> $words{$b} } keys %words
Note that the output is still the keys of the hash %words.
We actually want to sort from high to low, so swap $a and $b over to reverse the sort direction:
sort { $words{$b} <=> $words{$a} } keys %words
Since we're compiling a top ten list, we only want the first ten from our hash. It's possible to do this by taking a slice of the hash, but the easiest way is just to use an accumulator to keep count of how many entries we have in the top ten:
my %top_ten;
my $i = 0;
for (sort { $words{$b} <=> $words{$a} } keys %words) {
# $_ is the current hash key
$top_ten{$_} = $words{$_};
$i++;
last if $i == 10;
}
And we're done!
Please advice how to pass 3 variables in an array with relation.
#item = ($a , $b , $c);
#record = push(#array, #item);
I want to assign value in a #array so that if I look for any instance I should get value of all a,b,c.
Is there any way apart from comma to assign a value in array. like $a:$b:$c or $a>$b>$c
I need this because i am want to grep 1 record(a) and get (a:b:c)
#array1 = grep(!/$a/, #array);
expected output should be a:b:c
Thanks,
The question is not very clear. Maybe you should rephrase it.
However, I understand you want an array with groups of three elements.
You might want to use array references.
#item = ($a , $b , $c);
push(#array, \#item);
or
$item = [$a , $b , $c];
push(#array, $item);
Also, pushwon't return an array as you expect. Perldoc says:
Returns the number of elements in the array following the completed
"push".
Now if you want to filter these groups of three elements, you can do something like that:
my #output = ();
L1: foreach ( #array ){
L2: foreach( #$_ ){
next L1 if $_ eq $a;
}
push #output, $_;
}
Please note that if you want an exact match you should use the eq operator instead of a regex...
So i have been working on this perl script that will analyze and count the same letters in different line spaces. I have implemented the count to a hash but am having trouble excluding a " - " character from the output results of this hash. I tried using delete command or next if, but am not getting rid of the - count in the output.
So with this input:
#extract = ------------------------------------------------------------------MGG-------------------------------------------------------------------------------------
And following code:
#Count selected amino acids.
my %counter = ();
foreach my $extract(#extract) {
#next if $_ =~ /\-/; #This line code does not function correctly.
$counter{$_}++;
}
sub largest_value_mem (\%) {
my $counter = shift;
my ($key, #keys) = keys %$counter;
my ($big, #vals) = values %$counter;
for (0 .. $#keys) {
if ($vals[$_] > $big) {
$big = $vals[$_];
$key = $keys[$_];
}
}
$key
}
I expect the most common element to be G, same as the output. If there is a tie in the elements, say G = M, if there is a way to display both in that would be great but not necessary. Any tips on how to delete or remove the '-' is much appreciated. I am slowly learning perl language.
Please let me know if what I am asking is not clear or if more information is needed, thanks again kindly for all the comments.
Your data doesn't entirely make sense, since it's not actually working perl code. I'm guessing that it's a string divided into characters. After that it sounds like you just want to be able to find the highest frequency character, which is essentially just a sort by descending count.
Therefore the following demonstrates how to count your characters and then sort the results:
use strict;
use warnings;
my $str = '------------------------------------------------------------------MGG-------------------------------------------------------------------------------------';
my #chars = split '', $str;
#Count Characteres
my %count;
$count{$_}++ for #chars;
delete $count{'-'}; # Don't count -
# Sort keys by count descending
my #keys = sort {$count{$b} <=> $count{$a}} keys %count;
for my $key (#keys) {
print "$key $count{$key}\n";
}
Outputs:
G 2
M 1
foreach my $extract(#extract) {
#next if $_ =~ /\-/
$_ setting is suppressed by $extract here.
(In this case, $_ keeps value from above, e.g. routine argument list, previous match, etc.)
Also, you can use character class for better readability:
next if $extract=~/[-]/;
I'm looking for help sorting an array where each element is made up of "a number, then a string, then a number". I would like to sort on the first number part of the array elements, descending (so that I list the higher numbers first), while also listing the text etc.
am still a beginner so alternatives to the below are also welcome
use strict;
use warnings;
my #arr = map {int( rand(49) + 1) } ( 1..100 ); # build an array of 100 random numbers between 1 and 49
my #count2;
foreach my $i (1..49) {
my #count = join(',', #arr) =~ m/$i,/g; # maybe try to make a string only once then search trough it... ???
my $count1 = scalar(#count); # I want this $count1 to be the number of times each of the numbers($i) was found within the string/array.
push(#count2, $count1 ." times for ". $i); # pushing a "number then text and a number / scalar, string, scalar" to an array.
}
#for (#count2) {print "$_\n";}
# try to add up all numbers in the first coloum to make sure they == 100
#sort #count2 and print the top 7
#count2 = sort {$b <=> $a} #count2; # try to stop printout of this, or sort on =~ m/^anumber/ ??? or just on the first one or two \d
foreach my $i (0..6) {
print $count2[$i] ."\n"; # seems to be sorted right anyway
}
First, store your data in an array, not in a string:
# inside the first loop, replace your line with the push() with this one:
push(#count2, [$count1, $i];
Then you can easily sort by the first element of each subarray:
my #sorted = sort { $b->[0] <=> $a->[0] } #count2;
And when you print it, construct the string:
printf "%d times for %d\n", $sorted[$i][0], $sorted[$i][1];
See also: http://perldoc.perl.org/perlreftut.html, perlfaq4
Taking your requirements as is. You're probably better off not embedding count information in a string. However, I'll take it as a learning exercise.
Note, I am trading memory for brevity and likely speed by using a hash to do the counting.
However, the sort could be optimized by using a Schwartzian Transform.
EDIT: Create results array using only numbers that were drawn
#!/usr/bin/perl
use strict; use warnings;
my #arr = map {int( rand(49) + 1) } ( 1..100 );
my %counts;
++$counts{$_} for #arr;
my #result = map sprintf('%d times for %d', $counts{$_}, $_),
sort {$counts{$a} <=> $counts{$b}} keys %counts;
print "$_\n" for #result;
However, I'd probably have done something like this:
#!/usr/bin/perl
use strict; use warnings;
use YAML;
my #arr;
$#arr = 99; #initialize #arr capacity to 100 elements
my %counts;
for my $i (0 .. 99) {
my $n = int(rand(49) + 1); # pick a number
$arr[ $i ] = $n; # store it
++$counts{ $n }; # update count
}
# sort keys according to counts, keys of %counts has only the numbers drawn
# for each number drawn, create an anonymous array ref where the first element
# is the number drawn, and the second element is the number of times it was drawn
# and put it in the #result array
my #result = map [$_, $counts{$_}],
sort {$counts{$a} <=> $counts{$b} }
keys %counts;
print Dump \#result;
I am writing a Perl Script to find out the frequency of occurrence of characters in a message. Here is the logic I am following:
Read one char at a time from the message using getc() and store it into an array.
Run a for loop starting from index 0 to the length of this array.
This loop will read each char of the array and assign it to a temp variable.
Run another for loop nested in the above, which will run from the index of the character being tested till the length of the array.
Using a string comparison between this character and the current array indexed char, a counter is incremented if they are equal.
After completion of inner For Loop, I am printing the frequency of the char for debug purposes.
Question: I don't want the program to recompute the frequency of a character if it's already been calculated. For instance, if character "a" occurs 3 times, for the first run, it calculates the correct frequency. However, at the next occurrence of "a", since loop runs from that index till the end, the frequency is (actual freq -1). Similary for the third occurrence, frequency is (actual freq -2).
To solve this. I used another temp array to which I would push the char whose frequency is already evaluated.
And then at the next run of for loop, before entering the inner for loop, I compare the current char with the array of evaluated chars and set a flag. Based on that flag, the inner for loop runs.
This is not working for me. Still the same results.
Here's the code I have written to accomplish the above:
#!/usr/bin/perl
use strict;
use warnings;
my $input=$ARGV[0];
my ($c,$ch,$flag,$s,#arr,#temp);
open(INPUT,"<$input");
while(defined($c = getc(INPUT)))
{
push(#arr,$c);
}
close(INPUT);
my $length=$#arr+1;
for(my $i=0;$i<$length;$i++)
{
$count=0;
$flag=0;
$ch=$arr[$i];
foreach $s (#temp)
{
if($ch eq $s)
{
$flag = 1;
}
}
if($flag == 0)
{
for(my $k=$i;$k<$length;$k++)
{
if($ch eq $arr[$k])
{
$count = $count+1;
}
}
push(#temp,$ch);
print "The character \"".$ch."\" appears ".$count." number of times in the message"."\n";
}
}
You're making your life much harder than it needs to be. Use a hash:
my %freq;
while(defined($c = getc(INPUT)))
{
$freq{$c}++;
}
print $_, " ", $freq{$_}, "\n" for sort keys %freq;
$freq{$c}++ increments the value stored in $freq{$c}. (If it was unset or zero, it becomes one.)
The print line is equivalent to:
foreach my $key (sort keys %freq) {
print $key, " ", $freq{$key}, "\n";
}
If you want to do a single character count for the whole file then use any of the suggested methods posted by the others. If you want a count of all the occurances
of each character in a file then I propose:
#!/usr/bin/perl
use strict;
use warnings;
# read in the contents of the file
my $contents;
open(TMP, "<$ARGV[0]") or die ("Failed to open $ARGV[0]: $!");
{
local($/) = undef;
$contents = <TMP>;
}
close(TMP);
# split the contents around each character
my #bits = split(//, $contents);
# build the hash of each character with it's respective count
my %counts = map {
# use lc($_) to make the search case-insensitive
my $foo = $_;
# filter out newlines
$_ ne "\n" ?
($foo => scalar grep {$_ eq $foo} #bits) :
() } #bits;
# reverse sort (highest first) the hash values and print
foreach(reverse sort {$counts{$a} <=> $counts{$b}} keys %counts) {
print "$_: $counts{$_}\n";
}
I don´t understand the problem you are trying to solve, so I propose a more simple way to count the characters in a string:
$string = "fooooooobar";
$char = 'o';
$count = grep {$_ eq $char} split //, $string;
print $count, "\n";
This prints the number of $char occurrences in $string (7).
Hope this helps to write a more compact code
Faster solution :
#result = $subject =~ m/a/g; #subject is your file
print "Found : ", scalar #result, " a characters in file!\n";
Of course you can put a variable in the place of 'a' or even better execute this line for whatever characters you want to count the occurrences.
As a one-liner:
perl -F"" -anE '$h{$_}++ for #F; END { say "$_ : $h{$_}" for keys %h }' foo.txt