CODEWITHSUNDEEP
perlnumbers
pluton
pluton

Reputation: 242

replace small numbers in Perl

In a text file, I have many lines looking like (a,b,c) where a, b, and c are double precision real numbers, for instance (8.27605704077856,0.505526531790625,1.15577754382534e-05). Is there a simple way to replace numbers smaller than 10e-4 by 0 in Perl?

Edit: For instance, the text file to be treated looks like:

\plotinstruction[color,style,width]
points{
(8.27,0.5,1.1e-05)
(8.26,1,4.1e-06)
(8.25,1.5,3e-06)
}

and I want to write in a new file:

\plotinstruction[color,style,width]
points{
(8.27,0.5,0)
(8.26,1,0)
(8.25,1.5,0)
}

Upvotes: 0

Views: 222

Answers (2)

ruakh
ruakh

Reputation: 183456

You can write:

perl -pwe 's/\d[\d.e+-]+/$& < 0.001 && $& > -0.001 ? "0" : $&/ge' < INPUT > OUTPUT

(-p means to read in the input, one line at a time, into $_, run the program, print out $_, and loop again; -w enables warnings; -e means that the program is specified directly as a command-line argument; s/// is a regex-substitution; /g means that it's a "global" substitution; and /e means that the replacement-text should be treated as a full Perl expression, rather than as a string with mere variable interpolation.)

Upvotes: 0

Alex Reynolds
Alex Reynolds

Reputation: 96966

Perhaps I'm missing something, but perhaps use of map would help?

#!/usr/bin/env perl

use strict;
use warnings;
use Data::Dumper;

my @values = (8.27605704077856, 0.505526531790625, 1.15577754382534e-05);
my @filtered_values = map(($_ > 1e-4) ? $_ : 0, @values);

print Dumper \@filtered_values;

Results:

$VAR1 = [
          '8.27605704077856',
          '0.505526531790625',
          0
        ];

To parse input, you could use a regular expression to extract a comma-separated string of numbers, using split on that to get a Perl list to run map upon.

Upvotes: 3

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