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

Hi, i keep getting this error:

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

below are my codes:

function [output]=Trapzoid(a,b)

logN=1:8
N=zeros(1,8);
A=zeros(1,8);
for j=1:8
    N(j)=10^(logN(j));
    h=1/N(j);
    x=a:h:b;
    for i=1:N(j)+1 y(i)=exp(x(i));
    end
    for i=1:N(j)
        A(j)=A(j)+0.5*h*(y(i)+y(i+1));
    end

B(j)=log(abs(exp(1)-1-A(j)));

end

whenever i call for function Trapzoid(a,b) for eg, trapzoid(1,8) i will get the error: Undefined function 'Trapzoid' for input arguments of type 'double'. can anyone kindly advise on what actually went wrong? Much Thanks in advance!

Answer 1

[Jan]

Note:

x = a:h:b;
for i=1:N(j)+1
  y(i)=exp(x(i));
end

is less efficient than:

y = exp(a:h:b);

Answer 2

[Star Strider]

You have to save your ‘Trapezoid’ function in its own file called specifically ‘Trapezoid.m’ in your MATLAB search path. Note that MATLAB is case-sensitive, so calling it as ‘trapezoid(1,8)’ will throw the error. Call it as ‘Trapezoid(1,8)’, and if it is in your MATLAB path, you will not get that error.