Undefined function or variable 'npoints'.

It runs on matlab but the reason why it keep saying an error message is that i get wrong answer out of this function.

below is error message that i get this time

Undefined function or variable 'npoints'. Error in tutorial2 (line 7) midx=zeros(npoints,1); Error in Test1

i'm getting 75.0082 with this code on matlab

But the error percentage i'm supposed to have is around 0.0655

Could you see this again? thanks

function err = tutorial2(nPoints)
%% Midpoint rule for integral 4/(1 + x^2) from x = 0 to x = 1
% inputs:   - nPoints    number of points in domain
% outputs:  - err        percentage error (absolute value)
x=linspace(0,1,nPoints);
dx=x(2)-x(1);
midx=zeros(npoints,1);
numSol=0;
    for i = 0:nPoints-1
        midx(i)=(x(i)+x(i+1))/2;
        fvalue=4/(1 + midx(i)^2);
        numSol=numSol+fvalue;
    end
    numSol=numSol*dx;
    analyticalSol=pi/4;
    err=abs((analyticalSol-numSol)*100/numSol);
end

Answer 1

[Walter Roberson]

MATLAB is case sensitive. You used npoints on line 7, but you do not define that variable. You define nPoints with a capital P, which is a different variable.