Calculate Area under Surface

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!

[Walter Roberson]

It is not clear that you have a surface? What you show appears to be 2D. For 2D see polyarea()

[Detox]

Got your point now. My choice of words was just weird. Meant area! Thanks for pointing that out.

Answer 1

[Thorsten]

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