whats wrong with the code?

function fx=f(x)
for i=1:length(x)
    if x(i)<0
        fx(i)=x(i);
    elseif x(i)==0:pi/2;
        fx(i)=sin(x(i));
    else
        fx(i)=(sin(x(i)))     
    end
end
end

Answer 1

[Thorsten]

 x(i)==0:pi/2

compares x(i) to 0 and 1 (largest integer below pi/2) and gives the result in matrix of size 1x2. A matrix is considered to be true if all values are nonzero. Since x cannot be 0 and 1 at the same time, this never becomes true.

The code after else gives the same result as in the elseif before, so it does not make sense to differ between the two cases.

You don't need a for loop but you can use logical indexing to write your code, e.g.

fx(x<0) = x(x<0);
fx(x>=0 & x <= pi/2) = sin(x(x>=0 & x <= pi/2));
fx(x>pi/2) = -sin(x>pi/2);

Answer 2

[Star Strider]

I would re-code your elseif line to:

elseif (x(i)>=0) & (x(i) <= pi/2)

[Image Analyst]

Why & instead of &&?