Re: DensityPlot colours misbehaving
- To: mathgroup at smc.vnet.net
- Subject: [mg78737] Re: [mg78705] DensityPlot colours misbehaving
- From: Brett Champion <brettc at wolfram.com>
- Date: Sun, 8 Jul 2007 06:08:58 -0400 (EDT)
- References: <200707071005.GAA05698@smc.vnet.net>
On Jul 7, 2007, at 5:05 AM , Tim Birks wrote:
>
> I have Mathematica v6 and am running code that worked fine with v5.
> OS is
> Windows XP. Here's a particularly annoying unexplained difference
> between
> the two versions.
>
> DensityPlot[Exp[-x], {x, 0., 4.}, {y, 0., 4.}, ColorFunctionScaling ->
> False]
>
> behaves as expected, giving a nice gradual horizontal grading of
> colour from
> white on the left to blue/violet on the right.
>
> In contrast,
>
> DensityPlot[Exp[-x - y], {x, 0., 4.}, {y, 0., 4.},
> ColorFunctionScaling ->
> False]
>
> which should give a similar grading from lower-left to upper-right,
> instead
> gives a mostly blue/violet field with a pure white triangular wedge
> in the
> lower-left corner. The discontinuous jump between the two occurs
> roughly
> where x+y=1.4.
>
> Re-plotting with x and y running from 0 to 2 instead of 4 makes the
> white
> triangle appear smaller rather than bigger. Note the setting of
> ColorFunctionScaling means that the colour at a particular point (x,y)
> shouldn't depend on what's happening elsewhere; also note that the
> functions
> plotted are very simple, well-behaved and evaluate to between 0 and
> 1 in the
> ranges plotted.
>
> Can anyone please explain what is happening, how it can be fixed,
> and why it
> is not a bug?
>
> Apologies if this has been asked before. I have searched the posts
> available
> on my news reader and found nothing relevant.
The triangle at the bottom is being clipped by the automatic
PlotRange calculation.
Compare:
DensityPlot[Exp[-x - y], {x, 0., 4.}, {y, 0., 4.}]
DensityPlot[Exp[-x - y], {x, 0., 4.}, {y, 0., 4.}, ClippingStyle-
>Automatic]
DensityPlot[Exp[-x - y], {x, 0., 4.}, {y, 0., 4.}, PlotRange->All]
Brett Champion
Wolfram Research
- References:
- DensityPlot colours misbehaving
- From: "Tim Birks" <pystab@hotmail.com>
- DensityPlot colours misbehaving