Re^5: How to output matrix data from Math:;MatrixReal into a Hash or an Array

[davido]

It's not documented in the pod, but my own test runs indicated that the elements accessor is 1-based. Maybe that's how mathematics people like their matrices indexed... I dont know. But it seems to be how this module does it. Using zero will throw an out of range error.

[Laurent_R]

OK, Dave, thanks. I had looked into the POD and also did not see anything saying that indexing should be 1-based, that's why I was wondering and asked the question. But I did not have time then to try to install the module and test it. Thanks again.

[John007]

Folks thank you very much for your excellent help here. Truly appreciated.

I modified the code slightly to send data to a csv file as below.

use Text::CSV;
use Math::MatrixReal;

my $mref = [
  [ '5', '4', '4', '2', '4' ],
  [ '9', '6', '4', '4', '3' ],
  [ '2','73','96', '6', '8' ],
  [ '2', '4', '9','87', '8' ],
  [ '2', '4','10', '6', '8' ],
];

my $matrix = Math::MatrixReal->new_from_rows( $mref );

# At this point $matrix is a Math::MatrixReal object that
# resembles the one you showed us a Data::Dumper dump of.

my $csv = Text::CSV->new;
open my $FILE, ">", "./whatever.csv";

foreach my $row_num ( 1 .. 5 ) {
  $csv->print(*STDOUT, [ map { $matrix->element($row_num,$_) } 1 .. 5 
+] );
  print {*STDOUT} "\n";
  $csv->print($FILE, [ map { $matrix->element($row_num,$_) } 1 .. 5 ] 
+);
  print $FILE "\n";
}

[davido]

One possible bug I see: print {*STDOUT}, "\n";.

In the code I provided earlier in this thread, the $csv->print(....) was directing to STDOUT because I didn't want to set up an output file in an example script. Also, the newline was explicitly output because I noticed that one wasn't being inserted between CSV rows automatically by $csv->print(...).

Now in your solution you've got $csv->print($FILE...), but haven't directed the "print {*STDOUT} "\n"; to $FILE instead.

So you may want to look at the CSV it's outputting and verify that there's a newline being created between what you intend to be CSV rows. It may not be happening.

[John007]

Thank you very much for your help