Re: Calculate jackknife error from of each column of a multi-column file

I am very confused as to what this thing is supposed to do!
I ran just the first part of the code and this is what I get.
The n array is not multi-dimensional. There is not data in that array anyway in this first loop. $x[$n[$j]][$j] doesn't make sense to me.
Update: I guess $x[$n[$j]//=0][$j] = $column[$j]; "works", but I still don't quite get it.

#! /usr/bin/perl
use warnings; 
use strict;
use Data::Dumper;

my @n=0;
my @x;
my $j;
my $i;
my $dg;
my @x_jack;
my @x_tot=0;
my $cols;
my $col_start=0;

# read in the data
while(<DATA>)
{
  my @column = split();
  $cols=@column;
  foreach my $j ($col_start .. $#column) {
    $x[$n[$j]][$j] = $column[$j];
    $x_tot[$j] += $x[$n[$j]][$j];
    $n[$j]++;
  }
}

print "\n";
print "THE X ARRAY IS\n";
foreach my $rowref (@x)
{
   print "@$rowref\n";
}   
print "\n";
print "THE N ARRAY IS:\n";
print "@n";


=PRINTS:
Use of uninitialized value within @n in array element at line 22, <DAT
+A> line 1.
Use of uninitialized value within @n in array element at line 23, <DAT
+A> line 1.
Use of uninitialized value within @n in array element at line 22, <DAT
+A> line 1.
Use of uninitialized value within @n in array element at line 23, <DAT
+A> line 1.
Use of uninitialized value within @n in array element at line 22, <DAT
+A> line 1.
Use of uninitialized value within @n in array element at line 23, <DAT
+A> line 1.

THE X ARRAY IS
1.1 2.1 3.1 4.1
1.2 2.2 3.2 4.2
1.3 2.3 3.3 4.3
1.4 2.4 3.4 4.4

THE N ARRAY IS:
4 4 4 4
=cut


__DATA__
1.1 2.1 3.1 4.1
1.2 2.2 3.2 4.2
1.3 2.3 3.3 4.3
1.4 2.4 3.4 4.4
[download]

Comment on Re: Calculate jackknife error from of each column of a multi-column file Select or Download Code

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Re^2: Calculate jackknife error from of each column of a multi-column file by GrandFather (Saint) on Dec 16, 2020 at 02:21 UTC
Let's do `$x[$n[$j]][$j]` in bits: `foreach my $j ($col_start .. $#column) { my $nIndex = $n[$j]; $x[$nIndex][$j] = $column[$j]; $x_tot[$j] += $x[$nIndex][$j]; $n[$j]++; }` [download] The 'uninitialized value' error can then be fix by: `foreach my $j ($col_start .. $#column) { my $nIndex = $n[$j] // 0; $x[$nIndex][$j] = $column[$j]; $x_tot[$j] += $x[$nIndex][$j]; $n[$j]++; }` [download] Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond	[reply] [d/l] [select]
Re^3: Calculate jackknife error from of each column of a multi-column file by Marshall (Canon) on Dec 16, 2020 at 04:14 UTC
Yes, I see now that `$x[$n[$j]//=0][$j] = $column[$j];` is the answer. Thanks! The nested brackets confused my brain. I highly suspect that there is a more simple formulation of this part of the algorithm. For example, transforming a square matrix is not that hard and then you go row by row to get the column sums.	[reply] [d/l]


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