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List:       gnuplot-info-beta
Subject:    [PATCH 2/2] String variables (from datafile column)
From:       Ethan Merritt <merritt () u ! washington ! edu>
Date:       2002-08-16 4:55:14
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Hi all.

String variables in gnuplot: Patch 2 of 2

I have uploaded to SourceForge a pair of patches that implement two
aspects of handling string variables in gnuplot. Neither patch is 
intended to go right into CVS. These are proof-of-principle demos
of how string variables might work. They are both usable, however,
so I welcome feedback/suggestions/criticism from multiple testers.

Patch 2
-------

The second patch implements a different take on string variables.
It allows you to read in string values from selected columns of
a data file.  This is basic support that could be used for many
new plotting capabilities.  I have implemented only one simple
command by way of example:

Given a datafile containing something like:

# Label   X-position  Y-position
#
  Origin	0	0
  A		.1	.2
  B		.2	.1
  HiThere	.14	.3

Then
   plot 'datafile' using 2:3:1 with labels

will place centered labels "Origin" "A" "B" "HiThere" at
the (x,y) coordinates specified.  
'plot ... with labels' requires 3 columns of input:  x, y, string


Notes
-----

-  Patch 1 added  ./configure --enable-stringvariables
   Patch 2 can be applied independently from patch 1, but if you 
   haven't previously applied patch 1 then you will have to 
   manually add a line to ./config.h before running "make"
   	#define GP_STRING_VARS 1

- The underlying implementation touches enough bits of code that
  I may have overlooked side-effects.  As I said, this is not
  intended to go straight into CVS; it's a proof-of-principle 
  patch for people to play with.  But it does work :-)

- I think this support may be powerful enough so that some brave
  soul could re-implement time/date input in a much simpler manner.
  It's always nice when a new feature actually allows you to 
  remove or simplify old code.

- The sample 'plot ... with labels' implementation is pretty minimal.
  It should logically accept many of the normal label suboptions
  	plot ... with labels 
		{<justification>} {norotate | rotate {by <degrees>}}
		{"font,size"} {textcolor <colorspec>}

  This should be fairly easy, actually, because what I did was to
  trivially modify the existing routine place_labels( level ) to be
  place_labels( listhead, level ).  This allows you to pass an 
  arbitrary list of text_label structures to it for processing,
  which is exactly what I did.

-- 
Ethan A Merritt       merritt@u.washington.edu
Biomolecular Structure Center Box 357742
University of Washington, Seattle, WA 98195
phone: (206)543-1421
FAX:   (206)685-7002


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