Plot deviation of curve as shaded area inside

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A common question here in this forum is how to plot an area between two curves.
Here's one type of a common answer:
x = transpose(1:100);
y = x.^2;
curve1 = y*1.05;
curve2 = y*0.95;
x2 = [x flipud(x)];
inBetween = [curve1, curve2];
fill(x2, inBetween, 'k', 'LineStyle', 'none');
hold on;
plot(x, y, 'r', 'LineWidth', 2);
This is the result I get:
I used
to make the shaded area transparent.
What I would like to have is the area between those two curves shaded, since I want to show the red curve's deviation without having to use the green lines. Hence why I removed the Linestyle. But I get something like a linear fill between the starting and endpoint of the vectors.
How can I do that without too many lines of code? I'm afraid my laptop is at a certain limit with the actual length of vectors I have to plot (>800.000 values).
Also if you know if and how it's possible to alternate the shaded area like a zebra (white-black-white-black, etc) I'd appreciate if you tell me that!
Thank you!

Accepted Answer

Star Strider
Star Strider on 22 Jul 2022
I generally prefer patch to fill
x = transpose(1:100);
y = x.^2;
curve1 = y*1.05;
curve2 = y*0.95;
x2 = [x flipud(x)];
inBetween = [curve1 curve2];
patch([x; flip(x)], [inBetween(:,1); flip(inBetween(:,2))], 'k', 'LineStyle', 'none', 'FaceAlpha',0.25);
hold on;
plot(x, y, 'r', 'LineWidth', 2);
The approach to writing patch calls is to provide a defined area that the function can fill. Here, that is provided by plotting ‘curve1’ against ‘x’ and then plotting ‘flip(curve2)’ against ‘flip(x)’ completing the region to be filled.

More Answers (1)

Bjorn Gustavsson
Bjorn Gustavsson on 22 Jul 2022
Edited: Bjorn Gustavsson on 22 Jul 2022
Have a look at the file exchange. There there are multiple "shaded-error-plots". For example (without ordering of merit):
I have used a majority of these functions at different times to god result, now I have no memory of why one or the other was preferable.
Sokratis Panagiotidis
Sokratis Panagiotidis on 23 Jul 2022
This is what I get when using errorfill:
Unable to perform assignment because the indices on the left side are not compatible with the
size of the right side.
Error in errorfill (line 111)
E(:,n)= [y+temp(1,:) y(end:-1:1)-temp(2,end:-1:1)];
Error in Errorfill_Test (line 7)
errorfill(x, y, E3, '.');
My vector has almost 600 thousand entries so it's hard to tell what the problem is.

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