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How to shift the columns of a PDL matrix

by Anonymous Monk
on Jul 03, 2007 at 20:42 UTC ( [id://624781]=perlquestion: print w/replies, xml ) Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I have a PDL that is 8 columns by 120 rows.

I want to simply SHIFT all the columns to the right by 1 and insert a column of 0's for the first column. I would prefer to DROP the last column so I don't change the dimensions.

I think I can do it by slicing and gluing into a new PDL, but was wondering if there was any faster function that would hel me do it. I would prefer to use "inplace" if possible to minimize memory.

Also, I am aware of the SHIFTRIGHT function, but that doesn't seem to be doing the job. I believe that is a binary shift function.

Thanks!

  • Comment on How to shift the columns of a PDL matrix

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Re: How to shift the columns of a PDL matrix
by lin0 (Curate) on Jul 03, 2007 at 22:35 UTC

    Hi Anonymous Monk,

    you could use something like:

    $pdl = append(zeroes(1,$pdl->getdim(1)), $pdl(0:-2,:));

    [download]

    where $pdl is your 8 columns by 120 rows piddle

    Note: I am assuming you are using PDL::NiceSlice

    Cheers,

    lin0
[reply]
[d/l]

      since you don't want to grow your matrix, it is even simpler to use rotate to shift your columns and then insert your new data.

      $pdl=$pdl->rotate(1); 
$pdl(0,).=$new_data # your vector.

      [download]
[reply]
[d/l]

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