Getting area of selected area plot?

Is it possible to calculate the area selected with the area plot (example attached)?

Working with area plots allows to visually confirm how accurate my selection of points are, but I don't know how to get the filled area. I know that trapz is used for data under curve calculations, but my values are negative, plus I cannot see the exact data calculated with trapz, so I cannot confirm if I use it as I think I am.

---edit

Does this do the job?

trapz(selectedArea.YData, selectedArea.YData)

Answer 1

[Star Strider]

That won’t, but this might:

sel_area = trapz(selectedArea.XData, selectedArea.YData);

assuming of course that ‘selectedArea.XData’ exists.

[IJ]

XData and YData are properties of area.

Great, thanks! Do you know how I can plot area from trapz-calculated data? So, the other way around.

For example, if I wanted to confirm whether I calculated the correct selection. If I use the same y values and plot with area(), will it always reflect what trapz() calculated?

[Star Strider]

My pleasure.

I’m not certain what you’re asking. The area plotted with area should reflect what trapz calculated, however I have no idea how you would verify that. (One possibility might be the polyarea function.) Also, see if the related cumtrapz function will do what you want.