Re^4: adding an index column to a csv data file

Here is the code. The data has an extra blank in. The comment line does not work on the @multi_array, I suspect. I cannot figure out, too, how to print the added index as integers i.e. how to apply map to a part of the array.

#!/usr/bin/perl -w

# read data
my @multi_array; push @multi_array, [split(',', $_)] for <DATA>;
#@multi_array = map {s/\s//} @multi_array;

# add counter column
my $i = 0; (chomp $_->[1],$_->[2] = sprintf ("%d",$i++)) for @multi_ar
+ray;
#or
push @{ $multi_array[$_] }, $_ for 0 .. $#multi_array;

# modify columns
($_->[0] *= 1.0, $_->[1] /= 1.0) for @multi_array;

# screen output    
print join(",", map { sprintf "%e", $_ } @{$_}),"\n" for @multi_array;

__DATA__
0.00000000e+00, 2.41644835e+00
1.20048018e-04, 2.38938189e+00
2.40096037e-04, 2.36473989e+00
[download]

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Re^5: adding an index column to a csv data file by poj (Abbot) on Jun 03, 2019 at 17:43 UTC
You could build the array while reading the data `#!/usr/bin/perl use strict; use warnings; my @AoA = (); # ArrayOfArrays while (<DATA>){ s/\s//g; my @tmp = split ',',$_; $tmp[0] *= 1.0; $tmp[1] /= 1.0; $tmp[2] = $.; push @AoA,\@tmp; } printf "%e,%e,%d\n",@$_ for @AoA; __DATA__ 0.00000000e+00, 2.41644835e+00 1.20048018e-04, 2.38938189e+00 2.40096037e-04, 2.36473989e+00` [download] poj	[reply] [d/l]
Re^5: adding an index column to a csv data file by swl (Prior) on Jun 04, 2019 at 02:44 UTC
The solution by poj in 11100896 is cleaner as it handles the extra space at read time. However, you might only want to remove those following a comma, for which you can pass a regex to split. `push @multi_array, [split(/,\s/, $_)] for <DATA>;` [download] I also gave an incorrect example for the `map` in my previous post, as the code did not operate on array refs. The map can be replaced by code like this: `foreach my $row (@multi_array) { s/^\s+// foreach (@$row); }` [download] And it's a stylistic thing, but I would avoid using so many postfix loops, and only use the topic variable where it is clearer to do so (you might have good reasons to think differently, though). For example, this code snippet is getting difficult to read at the first pass (for me at least): `# modify columns ($_->[0] = 1.0, $_->[1] /= 1.0) for @multi_array;` [download] It is clearer as this (similar to what poj posted): `for my $row (@multi_array) { $row->[0] *= 1.0; $row->[1] /= 1.0; }` [download] And the nested foreach loops above could be: `foreach my $row (@multi_array) { foreach my $item (@$row) { $item =~ s/^\s+//; } }` [download]	[reply] [d/l] [select]