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List:       gnuplot-info-beta
Subject:    Re: Gnuplot logarithmic contours and palette
From:       Aapo Lankinen <aapo.lankinen () gmail ! com>
Date:       2005-06-08 10:52:24
Message-ID: 1118227944.7803.63.camel () localhost ! localdomain
[Download RAW message or body]

On Tue, 2005-06-07 at 19:52 +0200, Hans-Bernhard Bröker wrote:
> As so often, that depends on the background of the person doing the 
> expecting...
> 
> The right way of handling this would have been to do it like the other
> "tick series" things in gnuplot do it, i.e. like 'set xtics'.  Which 
> means the endpoints are numbers in the input format, but the increment
> is a *factor*, not an addition to the logarithm.

That's cool.  I made a new patch that implements it that way.


> So '5,2,200' should have delivered tics at (5,10,20,40,80,160)

Now the z ticks are exactly like that.  And the patch is even
simpler.  :-)


> Taking into account prior art, it is.  It just fails to be implemented 
> that way ;-(

Ok, thank you.  I don't have very deep knowledge of Gnuplot, so I didn't
realise that.  But now it's fixed, see the attached patch.

Best Regards,
Aapo Lankinen

-- 
Aapo Lankinen <aapo.lankinen@gmail.com>

["contourlog.patch" (contourlog.patch)]

Index: src/contour.c
===================================================================
RCS file: /cvsroot/gnuplot/gnuplot/src/contour.c,v
retrieving revision 1.25
diff -u -p -r1.25 contour.c
--- src/contour.c	23 Mar 2005 19:01:54 -0000	1.25
+++ src/contour.c	8 Jun 2005 10:46:53 -0000
@@ -234,7 +234,8 @@ contour(int num_isolines, struct iso_cur
 	    z += dz;
 	    break;
 	case LEVELS_INCREMENTAL:
-	    z = contour_levels_list[0] + i * contour_levels_list[1];
+	    z = AXIS_LOG_VALUE( FIRST_Z_AXIS, contour_levels_list[0] ) +
+	      i * AXIS_LOG_VALUE( FIRST_Z_AXIS, contour_levels_list[1] );
 	    break;
 	case LEVELS_DISCRETE:
 	    z = AXIS_LOG_VALUE(FIRST_Z_AXIS, contour_levels_list[i]);

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