# How do I make a RegionPlot for a matrix? [closed]

I have a 9 x 8 matrix containing values 0, 1, 2 and 3. I want to plot the region of matrix with value 3 with my parameters x -> {0, 0. 4} and y -> {0, 200}.

## closed as unclear what you're asking by user64494, MarcoB, Alex Trounev, David G. Stork, bbgodfreyJun 23 at 2:33

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• Would you please make clear what your "parameters" are supposed to mean? – Henrik Schumacher Jun 17 at 11:12
• I have solved basically 8 non linear equations by varying 2 parameters and stored the number of solutions in this matrix. I want to plot the region of my parameters where number of solution are 3. – Sushmita Pal Jun 17 at 12:22
• And the parameter x has changed gradually from 0 to 0.4 and y has changed from 0 to 200? – Henrik Schumacher Jun 17 at 13:30
• yes. I did try the code given by you but the plots are really thin. – Sushmita Pal Jun 17 at 13:41
• Have another look. I added how to use AspectRatio. – Henrik Schumacher Jun 17 at 13:48

If A is your matrix, you should try

MatrixPlot[1 - Unitize[A - 3]]


ArrayPlot is another alternative. You may find also the DataRange option of MatrixPlot and ArrayPlot interesting. For example (with reasonable AspectRation):

MatrixPlot[1 - Unitize[A - 3], DataRange -> {{0, 0.4}, {0, 200}}, AspectRatio -> 1]


plots the matrix scaled to the aspect ration 300/0.4. Of course, that won't be very helpful as the resulting plot is very thin.

To obtain a MeshRegion, you may also use

ArrayMesh[1 - Unitize[A - 3], DataRange -> {{0, 0.4}, {0, 200}}]