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Full Discussion: read line by line and calculate the co-presence of variables
Top Forums Shell Programming and Scripting read line by line and calculate the co-presence of variables Post 302714771 by DGPickett on Friday 12th of October 2012 03:43:27 PM
Old 10-12-2012
Well, the SQL flavored solution is to decompose the table into a simpler table, columns into rows, with a union in a derived table, for instance:
Code:
Var Obs
A 1
A 2
A 3
B 2
C 1

Now you can join that table to itself, where a.obs=b.obs and (to avoid self and duplicate corelations, if you care) a.var < b.var

In SQL, when someone puts the cells of like entities that should be many rows into columns, a rotated array, you need unions to view the few rows many columns as one column many rows. Conversely, if you need to turn cells from many rows into columns of one row, you need to use joins. It is a common RDBMS design error to put arrays horizontally in rows when they belong vertically in one column many rows.

Now if we start talking lines and columns, 'union' is concatenate (cat, >> or just multiple passes in a subshell), 'join' is, surprise, 'sort' and 'join'; 'where' is in the join or grep. Deciding 'A' < 'B' is more a perl chr()/ord() or C question, but you were accepting self and duplicate matches above.
 

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LEARN ABOUT PHP

_request

_REQUEST(3)								 1							       _REQUEST(3)

$_REQUEST - HTTP Request variables

	An associative array that by default contains the contents of $_GET, $_POST and $_COOKIE.

       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.3.0	|						    |
       |	|						    |
       |	|  Introduced request_order. This directive affects |
       |	| the contents of $_REQUEST.			    |
       |	|						    |
       | 4.3.0	|						    |
       |	|						    |
       |	|  $_FILES information was removed from $_REQUEST.  |
       |	|						    |
       | 4.1.0	|						    |
       |	|						    |
       |	|		Introduced $_REQUEST.		    |
       |	|						    |
       +--------+---------------------------------------------------+
       Note

	      This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes  throughout	a  script.
	      There is no need to do global $variable; to access it within functions or methods.

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PHP Documentation Group 													       _REQUEST(3)
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