MATLAB: I need help using the quad function

definite integralintegrationquad

When using the quad function to integrate, I am getting the error:

FUN must be a function, a valid string expression, or an inline function object.

I am trying to integrate the polyval.

Here is my code. How do I fix it to integrate the function and avoid this error message?

function [ A ] = func( x )

clear all clc

A=5;

B=25;

x=[0 10];

y=[A B];

p=polyfit(x,y,1);

func=polyval(p,x);

q=quad(func,0,10)

end

To integrate a vector (or matrix in one of its dimensions), use the trapz function. The quad, integral, and related functions integrate functions.

integral() passes in a vector of values and expects one result for each element of the vector. You need to vectorize:

function y = step_fun(t)
  y = zeros(size(t));
  y(t>=0) = 1;

Or more compactly,

function y = step_fun(t)
   y = t >= 0;

which can be done as

step_fun = @(t) t >= 0;

L = 10;
out = quad(@(z)L*z./(L/2+z).*exp(-2*z/L),0,10);