使用tr ///运算符计算字符串中的字母 [英] Using tr/// operator to count letters in a string

问题描述

我想在序列或字符串中计算A的数量，C和G的数量。我写了以下代码。

I would like count number of A's, C's and G's in a sequence or string. I have written the following code.

但是当我打印的值，只有A的打印。 C和G显示为零。
在下面的代码中，我在评估A的第一个，但如果我通过评估C的第一次切换顺序，我得到C的值，但现在A和G的打印为零。

But when I print the values, only A's get printed. C's and G's are displayed as zero. In the code below I'm evaluating A's first, but if I switch the order by evaluating C's first, I get the values of C, but now A's and G's are printed out as zero.

任何人都可以告诉我我的代码有什么问题？谢谢！

Can anyone tell me what is wrong with my code? Thanks!

#! /usr/bin/perl

use strict;
use warnings;

open(IN, "200BP_junctions_fasta.faa") or die "Cannot open the file: $!\n";
while(<IN>) 
    next if $_ =~ /\>/;
    my $a = ($_ = tr/A//);
    my $c = ($_ = tr/C//);
    my $g = ($_ = tr/G//);
    print "A:$a, C:$c, G:$g\n";
}

文件如下所示：

> A_Seq  
ATGCTAGCTAGCTAGCTAGTC  
> B_Seq  
ATGCGATCGATCGATCGATAG  

推荐答案

将 $ _ = tr / 更改为 $ _ =〜tr / 。此外，您缺少了和的开放括号。

Change your $_ = tr/ to $_ =~ tr/. Also, you're missing an open brace for your while.

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