Calculate Area under Surface

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Detox
Detox 2016-7-16
编辑： Thorsten 2016-7-18
Hi guys,
does anybody know how I can calculate the area under the given curve. I already used a horizontal line at approx. 4.58 to limit my desired area with the following code.
area(x1, max(x1, tmp_1), tmp_1, 'EdgeColor', 'none', 'FaceColor', [.7 .7 .7])
Just to check if my area is the one I really want to calculate. My question now is:
With which approach can I calculate the area and generate an output?
Would you do this with
trapz
But I am not sure about the range for trapz? Really appreciate your help!
  2 个评论
Walter Roberson
Walter Roberson 2016-7-16
It is not clear that you have a surface? What you show appears to be 2D. For 2D see polyarea()
Detox
Detox 2016-7-17
编辑：Detox 2016-7-17
Got your point now. My choice of words was just weird. Meant area! Thanks for pointing that out.

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回答（1 个）

Thorsten
Thorsten 2016-7-18
编辑：Thorsten 2016-7-18
x = 1:60;
y = exp(-0.1*x); % sample data
plot(x,y)
trapz(y) % area under the curve
Note that if the curve is below zero, this part counts as negative area.
trapz(-y)
An if you have sampled your y data every dx, with a dx ~= 1, your area is
trapz(y)*dx

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