MATLAB: How to shade the plot into different colors in MATLAB 7.9 (R2009b)

colorfillMATLABpatch

I am using the PLOT command to plot a few points like this:

figure,plot([0:0.1:1],[0:0.1:1])
hold on,plot(rand(10,1),rand(10,1),'*')

I am interested in seeing points above and below the X= Y line, and for this, I would like the top portion of this line to be colored red and the bottom portion to be colored blue.How can I do this?

Best Answer

In order to achieve this functionality, use the FILL command with the 'FaceAlpha' parameter in the following way:

figure,plot([0:0.1:1],[0:0.1:1])
hold on,plot(rand(10,1),rand(10,1),'*')
fill([0 1 0] , [0 1 1],'r','FaceAlpha',0.5)  %Fill the top triangle red
fill([0 1 1] , [0 1 0],'b','FaceAlpha',0.5)  %Fill the bottom triangle blue

To read more about the FILL command, please visit here:

https://www.mathworks.com/help/matlab/ref/fill.html

Related Solutions

MATLAB: How to write a Matlab script that is able to output images of triangles based on the size input? The following shows the half of a triangle but i can’t find a way to make an isolated triangle. (The size you can put at range 3 – 8 )

What types of triangles do you need? And what will they be used for?

If you need very basic triangles, you could use the triangular marker types for scatter plots:

[y,x] = meshgrid(1:4);
z = 250:200:1000; %size of markers
figure;
axis([0 5 0 5]);
hold on;
scatter(x(1,:),y(1,:),z,'r^','FaceColor','r');
scatter(x(2,:),y(2,:),z,'gv','FaceColor','g');
scatter(x(3,:),y(3,:),z,'b<','FaceColor','b');
scatter(x(4,:),y(4,:),z,'m>','FaceColor','m');
hold off;

Or, if you need to create triangles with more variation in size, shape, and vertex position, try using insertShape:

figure;
I = zeros(100,'uint8');
J = insertShape(I,'filledpolygon',randi([10 90],1,6),'Color','white','Opacity',1);
imshow(J);

Note that this option actually embeds the triangle in an image. If you want to have a triangle "object", try using patch:

figure;
x = randi([0 10],1,3); %random x-coordinates
y = randi([0 10],1,3); %random y-coordinates
patch(x,y,'green');

MATLAB: Problem with markers & dashed lines in figures containing both plot and fill

This is a problem with the opengl renderer. When you have a transparency, you are using opengl, and it can be buggy. To see the difference, click on that figure then:

set(gcf,'render','painters')

Notice the legend looks fine but your transparency has gone away. I am not sure if there is a fix for this.

Best Answer

Related Solutions

MATLAB: How to write a Matlab script that is able to output images of triangles based on the size input? The following shows the half of a triangle but i can’t find a way to make an isolated triangle. (The size you can put at range 3 – 8 )

MATLAB: Problem with markers & dashed lines in figures containing both plot and fill

Related Question