How can I generate a vectorized version of a piecewise-defined function for use in the QUAD or QUADL for functions?

I have created the following function that represents a piecewise-defined function:

   function y = pieces(x)

   if (0<=x)&(x<=1)

       y = 3*x - 2;

   elseif (1<x)&(x<=2)

       y = 2 - x;

   else

       y = 0;

   end

However, when I specify this function to the QUAD function:

quad(@pieces,-5,5)

I get the following error:

 ??? Index exceeds matrix dimensions.

 Error in ==> quad.m

 On line 67  ==> if ~isfinite(y(7))

Answer 1

[MathWorks Support Team]

The QUAD function expects the integrating function to input a vector and return a vector of the same size. The given function will accept a vector, but returns a scalar.

Update your function with the vectorized version of this piecewise-defined function which is:

function y = pieces(x)

I1 = (0 <= x) & (x < 1); 

I2 = (1 <= x) & (x < 2);

I3 = ~I1 & ~I2;

y = x; % Create y same size as x

y(I1) = 3*x(I1) + 2;

y(I2) = 2 - x(I2);

y(I3) = 0;