How to fill a graph exclusing given points?

If a graph has a cluster of points, I want the graph to be filled such that every other point except the cluster is coloured

[Adam Danz]

What do you mean by "I want the graph to be filled"? A solid background color? Filled with random points? A picture would work....

[Anna]

A solid background color would do

[Adam Danz]

How do you define the cluster? Is it circular? Oval? Do you have the parameters that define the bounds of the cluster? Again, a quick drawing or example picture would help.

Just trying to avoid investing time into creating a solution that won't be useful.

[Anna]

[rough93]

Based on an irregular shape, do you have the function of the lines between each point? You'd need to either have or generate those functions and then the easiest way would be to make a test for each point for every row/column (using a for loop)to see whether it is above or below (and left or right of) that function. All pixels that meet the criteria you can simply apply a color to.

[Anna]

I used the boundary and fill function to colour the cluster in MATLAB but it's they don't work for the space in "green".

I will try for loop. Thank you.

[Adam Danz]

If you have the coordinates of the cluster boundary, you can use the axis limits to create a match with the empty cluster region.

Here's an example

https://www.mathworks.com/matlabcentral/answers/12335-patch-with-holes#answer_321823

[Anna]

Thank you

Answer 1

[Steven Lord]

Let's make a random (well, not so random, more arbitrary) polygon.

A = nsidedpoly(5, 'Center', [1 1], 'Radius', 2);

If you wanted to enclose a non-regular region you can use polyshape instead of nsidedpoly (in fact nsidedpoly makes a polyshape.) Plot it and make it red.

p = plot(A, 'FaceColor', 'r');

Find the axes that contains the plotted polygon.

ax = ancestor(p, 'axes');

Make the axes background cyan.

ax.Color = 'c';

Because the plotted polygon is translucent you can see the cyan background "through" it, which makes it look very not red. Let's make it fully opaque so you can't see the background through it.

p.FaceAlpha = 1;

There we go; red pentagon on a cyan background.