Undefined function 'int' for input arguments of type 'double'.

I am trying to integrate a function of propulsive power (positive values only) with respect to time to give energy. The propulsive power is in the form of a 10321x1 double matrix. The time is to range between 0 and 1032.1 seconds. The code I am inputting is as follows:

E = integral(Px_Pos,0,1032.1)

I am greeted with the error: Undefined function 'int' for input arguments of type 'double'. Can someone please help me?

I am new to MatLab and so my apologies if this is a trivial question.

Answer 1

[Torsten]

Use "trapz" instead of "integral".

Best wishes

Torsten.

[Mathew Lindley]

Hi Torsten,

Many thanks for the quick reply.

Using 'trapz' I received the following:

Energy = trapz(Px_Pos,0,1032.1) > In trapz (line 37) Warning: ORDER contains non-integer indices. This will return an error in a future release. Error using message Error filling holes for MATLAB:trapz:LengthXmismatchY. Floating point numbers are not allowed as holes. They should be converted to character vectors.

Error in trapz (line 57) error(message('MATLAB:trapz:LengthXmismatchY',dim));

[Torsten]

Put your times in a 10321x1 vector T as well as the propulsive power in a 10321x1 vector P.

Then call "trapz" as

I = trapz(T,P).

Best wishes

Torsten.

[Mathew Lindley]

Torsten,

Many thanks for your help, this has worked.

Kind regards, Matt