Re: ArrayPlot coordinates scaling for overlays

• To: mathgroup at smc.vnet.net
• Subject: [mg109202] Re: ArrayPlot coordinates scaling for overlays
• From: Patrick Scheibe <pscheibe at trm.uni-leipzig.de>
• Date: Fri, 16 Apr 2010 05:54:03 -0400 (EDT)

```Hi,

use DataRange to tell Mathematica about the rectangle where your
ArrayPlot is in

img = Import["http://sipi.usc.edu/database/misc/5.1.12.tiff";];
Show[{
ArrayPlot[img[[1]], DataRange -> {{0, 2 Pi}, {-1, 1}},
ColorFunction -> GrayLevel],
Plot[Sin[x], {x, 0, 2 Pi}]
}]

and you can overlay different plots.

Cheers
Patrick

On Wed, 2010-04-14 at 23:13 -0400, fd wrote:
> All
>
> This seems a simple problem I not finding an easy solution.
>
> I have a plot obtained from an ArrayPlot, for which the coordinates
> are the indexes of the matrix being plotted; I want to overlay to this
> plot some other plot, say, from DensityPlot. I have to tell
> Mathematica that the bottom left corner of the ArrayPlot is {xi,yi}
> and the upper right is {xf,yf}.
>
> It would be nice as well to know how you could do this with a raster
> image in general.
>
> I was trying to use ListDensityPlot, but for the specific problem I
> dealing with it is excruciatingly slow.
>
> I'm also working to re-scale the FrameTicks by defining a new
> ArrayPlot function, with limited success. Below the code I'm working
> on.
>
> Felipe
>
> arrayPlotScale[array_List, {xmin_, xmax_}, {ymin_, ymax_}] :=
>  Module[{deltas =
>     Reverse[{ymax - ymin, xmax - xmin}/Dimensions[array]],
>    n = Dimensions[array] // Reverse},
>   ArrayPlot[array,
>    FrameTicks ->
>     Reverse[{Table[{i, xmin + i deltas[[1]] }, {i, 0, n[[1]], 20}],
>       Table[{n[[2]] - i, ymin + i deltas[[2]]}, {i, 0, n[[2]],
> 10}]}]]]
>
> test = Table[i j, {i, 1, 100}, {j, 100, 1, -1}];
>
> arrayPlotScale[test, {0, 16}, {0, 100}]
>

```

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