Numerical integral at irregular intervals of scattered data

I have two vectors x,y of equal size (for example 5000 elements), ranging from 0 to 1 (containing scattered data, but already sorted in increasing order). I want to evaluate the numerical integral of y(x) for each interval defined by the following vector [0 0.27 0.38 0.46 0.53 0.60 0.65 0.71 0.76 0.80 0.85 0.89 0.93 0.96 1] by means of trapz. How can I obtain the vector of evaluated integrals at each interval?

Answer 1

[Torsten]

First use cumtrapz for cumulated integration, then use interp1 to interpolate to your vector:

z=cumtrapz(x,y);
zinter=interp1(x,z,xinter);

where xinter=[0 0.27 0.38 0.46 0.53 0.60 0.65 0.71 0.76 0.80 0.85 0.89 0.93 0.96 1]

Best wishes

Torsten.

[matnewbie]

I tried your method, but I got this error message:

Error using griddedInterpolant The grid vectors are not strictly monotonic increasing.

[Torsten]

You wrote you already sorted x in increasing order...

Best wishes

Torsten.

[matnewbie]

Thank you, but I posted a new question, since I am not interested anymore in irregular intervals.