[Buffalo-pm] Question: How to iterate through 2 arrays and merge columns

[Shankar, Ganesh]

Hello All,

Again,thanks for taking the time to walk me through this.

As you suggested, I started working with the data as strings.  This made it conceptually easier to deal with and I wanted to avoid thinking about anonymous arrays at this point.

The approach at this point looks like this:-


open( REDOPEN, $red_file ) or die $!;
	print "opened " . $red_file . "\n";
	my $i;
	for ( $i = 0 ; $i < 21 ; $i++ ) {
		print "looping through header line $i \n";
		<REDOPEN>;
	}
	my @red = <REDOPEN>;
	foreach my $red_line (@red) {
		our @red_items = split( '\t', $red_line );
		push(our @red_elements,		
				$red_items[6]. "\t", $red_items[7]."\t",
				$red_items[8]. "\t", $red_items[9]. "\t"
		);
	}    #end foreach my $red_line

...There is a similar block for dealing with green data...
Here is the loop to concatanate the two strings together.

for (my $i= 0;$i <= $#red_elements; $i++){
			print OUTFILE  $red_elements[$i],$green_elements[$i];
			}


When I execute this, I get the following error:-

Variable "@red_elements" is not imported at line 80 (#1)
    (F) While "use strict" in effect, you referred to a global variable that
    you apparently thought was imported from another module, because
    something else of the same name (usually a subroutine) is exported by
    that module.  It usually means you put the wrong funny character on the
    front of your variable.

Line 80 corresponds to this line: for (my $i= 0;$i <= $#red_elements; $i++){

I thought declaring @red_elements to be 'our' made it available throughout the program?  Is scoping the problem?

I thought I'd cheat, and turned off 'use strict'.

At that point, I got an uninitialized variable error pointing to this line:

push(our @red_elements,

Looks like the two errors are related and solving the first error should take care of the uninitialized variable error.

Any pointers?  Where can I read about this?

Thanks again.

-Ganesh Shankar



-----Original Message-----
From: Jim Brandt [mailto:cbrandt at buffalo.edu]
Sent: Wed 7/6/2005 8:11 AM
To: Shankar, Ganesh
Cc: buffalo-pm at pm.org
Subject: Re: [Buffalo-pm] Question: How to iterate through 2 arrays andmerge columns
 
I think my example mixed a few variable names as well, and that may  
have confused things.

Looking at your original code, you are doing:

> push(our @red_elements,
> ($red_items[6], "\t", $red_items[7], "\t",
> $red_items[8], "\t", $red_items[9], "\n"
> )
> );

The parentheses (which I didn't see before) will create an anonymous  
array in each element of @red_elements. This can work for you since  
you've created a 2-dimensional array, which is really a table. So I  
think if you modify my code to do this:

for (my $j=0;$j<=$#red_elements;$j++){
   # Iterate through outer loop, one row at a time.
   for ( my $i=0; $i <= 7; $i++ ){
     # You have eight columns, so this will go through each column  
and print it.
     print OUTFILE $red_elements[$j][$i];
   }

   # Repeat for green_elements.
   for ( my $i=0; $i <= 7; $i++ ){
     # You have eight columns, so this will go through each column  
and print it.
     print OUTFILE $green_elements[$j][$i];
   }

} # End outer loop.

Note that you'll need to modify your code building the red_elements  
since you are currently putting a new line as the last element and I  
think you want a tab.

That should work, but is a bit convoluted. I would simplify your  
earlier step to make it just a string rather than 8 elements in an  
array. For example:

push(our @red_elements, $red_items[6] . "\t" . $red_items[7] . "\t" .  
$red_items[8] . "\t" . $red_items[9] . "\t" );

The dot is the string concatenation operator, so it will push all of  
that together into a single string. I think if you do it this way, my  
first example will work.

Basically, it's playing with data structures two different ways.

For what it's worth, I think Kevin's suggestion was the quickest and  
cleanest, but you don't get to play with data structures in perl. :)

Good luck.

Jim

On Jul 5, 2005, at 10:33 PM, Shankar, Ganesh wrote:

> Your suggestions were on the right track but maybe I wasn't clear  
> as to what I wanted.  I need 4 cols from red followed by 4 cols  
> from green.  The following code gives me 4 pairs of red(no space) 
> green(tab)(tab).
>
> I tried:
> <code>
>     for (my $j=0;$j<=$#red_items;$j++){
>     push(@intermediate, $red_items[$j],$green_items[$j]);
>     }
> print OUTFILE @intermediate;
> </code>
>
> What results is:
> $red_items[6](no space)$green_items[6](2 tabs)$red_items[7](no  
> space)$green_items[7]
> (2 tabs)$red_items[8](no space)$green_items[8](2tabs)$red_items[9] 
> (nospace)$green_items[9]

==========================================
Jim Brandt
Administrative Computing Services
University at Buffalo




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