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msanchez78 has asked for the wisdom of the Perl Monks concerning the following question:

seeking the wisdom of the perl monks ...

within R i submit this code: 

> data <- c("2016-03-15 13","2016-03-16 23","2016-03-17 06","2016-03-1
+8 15","2016-03-19 08","2016-03-20 21")
> datevec <- strptime(data,"%Y-%m-%d %H")
> difftime(datevec[-length(datevec)],datevec[-1],units="hours")

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which correctly produces this output:
Time differences in hours
1 -34 -7 -33 -17 -37

notice the two lines. now, in perl i have this code:
$R->set( 'data', "2016-03-15 13","2016-03-16 23","2016-03-17 06","2016
+-03-18 15","2016-03-19 08","2016-03-20 21" );
$R->run( q`datevec <- strptime(data,"%Y-%m-%d %H")` );
$R->run( q`xx <- difftime(datevec[-length(datevec)],datevec[-1],units=
+"hours")` );
@Rres = $R->get('xx');
print Dumper(\@Rres);

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which correctly produces this result:
$VAR1 = [
          [
            'Time',
            'difference',
            'of',
            'hours'
          ]
        ];

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the problem is that no matter what i do i cannot get to the second output line from R ... the line 1 -34 -7 -33 -17 -37

any suggestion on how i can get to the second (and in many cases n-number) of subsequent output lines from R? thanks!

Replies are listed 'Best First'.
Re: Entire Results from R
by Veltro (Hermit) on Feb 20, 2019 at 16:31 UTC

    Can you try to print the raw result? Maybe this will help to see what is wrong.

       my $tmp_str = $R->run(qq`print($varname)`);
   print $tmp_str . "\n" ;

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    I got the previous line from the 'get' method of the module Statistics::R which I assume you are using. The 'get' method is doing a whole bunch of other stuff (which may cause the problem), so this line might show the entire result. Another small thing is that you are using @Rres = $R->get('xx'); and the method is returning a array reference. Although it is not entirely incorrect I do suggest using my $Rres = $R->get('xx'); print Dumper($Rres); instead

    Further I don't know much about R

    edit: Oh, and $varname should be 'datevec' or 'xx' or in this case of course.

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      hi ... thank you for your prompt reply. i tried 
         my $tmp_str = $R->run(qq`print($varname)`);
   print $tmp_str . "\n" ;

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      the result is the same --- the first line only:

      Time difference of hours

      yikes!
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        I would go in and manually edit this line to 1–

        use constant DEBUG      => 0;                     # debugging messages

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        And see what you get.

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Re: Entire Results from R
by haukex (Archbishop) on Feb 21, 2019 at 09:14 UTC

    Your use of $R->set() is incorrect: to set multiple values, you have to pass an arrayref: $R->set( 'data', ["2016-03-15 13","2016-03-16 23","2016-03-17 06","2016-03-18 15","2016-03-19 08","2016-03-20 21"] ); Then the code works for me.

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      ++haukex I put together a short script to confirm that your solution works (I was curious about Statistics::R since I had not used it before). This code, 
      #!/usr/bin/env perl

use Statistics::R;
use Data::Dumper;

# Create a communication bridge with R and start R
my $R = Statistics::R->new();

$R->set(
    'data',
    [
        "2016-03-15 13",
        "2016-03-16 23",
        "2016-03-17 06",
        "2016-03-18 15",
        "2016-03-19 08",
        "2016-03-20 21"
    ]
);

$R->run( q`datevec <- strptime(data,"%Y-%m-%d %H")` );
$R->run( q`xx <- difftime(datevec[-length(datevec)],datevec[-1],units=
+"hours")` );
@Rres = $R->get('xx');

print Dumper(\@Rres);

exit;

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      Gives this output, 
      $VAR1 = [
          [
            '[1]',
            '-34',
            '-7',
            '-33',
            '-17',
            '-37'
          ]
        ];

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        Thanks for the example! I also submitted a pull request that adds a "too many arguments" error to ->set.

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