MATLAB Answers


Vary the thickness of plot

Asked by Zeynab Mousavikhamene on 10 Nov 2019
Latest activity Commented on by Walter Roberson
on 11 Nov 2019
I am potting multiple plots on one axis and I want to vary the thickness of plots based on their absolute value.
How can I do that?

  1 Comment

Can you provide some example, to understand what do mean by "absolute value" of a plot?

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3 Answers

Answer by Walter Roberson
on 11 Nov 2019

In MATLAB, any one primitive line object, or any one mesh or surface or patch's edge, has constant width. You can do a bit with arrow heads, but not very much, really.
A line can be broken up into line segments that are created with individual line object, each of which is a constant size. But if you have widths computed according to the value associated with a point, then you need to decide how you are going to compute the width between the point and the previous point, or the point and the next point.
About the only way I can think of to get variable thickness of lines is to use patch objects to draw the lines, using trapazoids, such as (x1, y1+width1/2) to (x2, y2+width2/2) to (x2, y2-width2/2) to (x1, y1-width1/2) back to (x1, y1+width1/2) and color that face with the color to be associated with the line.
There is a file exchange contribution for drawing lines with variable color by using patches, that you could probably adapt.


What you mean by width1/2 or width2/2? and what is patch here?
By the way can I change the size of points by their absolute value? The bigger the absolute value, the larger diamter would that specific point have.
Walter Roberson
on 11 Nov 2019
patch is which is a fundamental graphics routine for creating arbitrary lines and faces.
You want to vary your line width according to absolute value of something. You have information associated with each point that can be used to compute the corresponding width for each point. Suppose that you have computed all of those values and stored them in a variable named Widths, one entry for each X, and assuming you have the same number of Y. Then
xt = x(:);
xv = [xt; flipud(xt)]; %up to maximum, back to beginning
yt = y(:);
yv = [yt - Widths(:)/2; flipud(yt + Widths(:)/2)];
fill(xv, yv)
This draws a variable-width box around the coordinates.
By the way can I change the size of points by their absolute value?
scatter() can easily handle different size of points each, but any one primitive line object can only have a constant-sized point.
It is relatively easy to do something like
plot(x, y);
hold on
scatter(x, y, Widths);
hold off

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Answer by Akira Agata
on 11 Nov 2019

How about using daspect function?
The following is an example.
d1 = rand(1,10);
d2 = rand(1,10)*10;
ax1 = subplot(1,2,1);
ax2 = subplot(1,2,2);
daspect(ax1,[1 1 1]);
daspect(ax2,[1 1 1]);


Walter Roberson
on 11 Nov 2019
I am not sure how this relates to absolute values?
@Akira Agata Thanks for the suggestion but I meant the thickness of plot not the size of axis.
Image Analyst
on 11 Nov 2019
That's why I suggested 'LineWidth" in my Answer. But your question is very ambiguous -- that's why you may not have the answer you want yet. Please try to post a screenshot of exactly what you'd like to see. Use the green frame icon.

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Answer by Image Analyst
on 11 Nov 2019

Do you mean LineWidth of the curve your data makes when plotting it with plot(), like
lineWidth = round(min([1, mean(y)]); % or 2, 3, 4 or whatever width you want
plot(x, y, 'LineWidth', lineWidth);


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