How to set FaceAlpha of area plot

Hi, I run in some issues when I try to set the transparency of an area plot. I can set the transparency of the histogram but not of the area plot. Is this a bug? Version: R2015a 8.5.0.197613.

This is the code I used:

clc;clear;
figure
h = histogram(1:10);
h.FaceAlpha = 0.2;
grid
figure
a = area(1:10);
grid
a.FaceAlpha = 0.2;

This is the warning I get: "No public field FaceAlpha exists for class matlab.graphics.chart.primitive.Area."

Thanks

Answer 1

[Star Strider]

Your code works correctly for me in R2016a.

As an alternative, you can use the patch function:

figure(2)
a = patch([1:10 10:-1:1], [1:10 zeros(1,10)], 'b');
grid
a.FaceAlpha = 0.2;

Note that you have to change your code to define the patch object, here adding a zeros vector to complete it.

[Lorenzo]

Hi, patch works fine. I suppose there is a problem with my version, since area and bar plot seem to lack a facealpha option.

Thanks!

[Star Strider]

My pleasure!

It may not be a problem, that feature was likely added in a later version.

Also, in a more general expression, the patch call for the sort of plot you want is:

a = patch([1:10 flip(1:10)], [1:10 zeros(1,10)], 'b');

Note that you need to provide a ‘return path’ in your x-vector in patch, the reason for the flip call (you can also use fliplr). The y-vector has to have upper and lower border limits that match the x-vector.

[Lorenzo]

Thanks again! In the end I sticked with the area plot without alpha.. I did not want to change all the data to patches, but a first try showed good results.

[Star Strider]

My pleasure.

You can also see if the fill function implements the ‘alpha’ parameter. It requires that you define a closed polygon for your data but may be easier to use with your data.

One option is to create your own function that implements the patch function and then call it in your plots. That way you would not have to change all your data, you simply call your function in each plot. You could probably do that with an anonymous function.

Answer 2

[John BG]

In R2016a

your code works fine for both graphs.

Yet, you may want to control transparency separately:

clc;clear;
figure(1);
h = histogram(1:10);
h.FaceAlpha = 0.2;
grid
figure(2);
a = area(1:10);
grid
a.FaceAlpha = 0.8;

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thanks in advance

John

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