Quick matlab question regarding if statements/for loops

I need to write a code for if x>a then calculate (x-a)^n, if x<=a output 0. I figure my initial issues were that since x can be scalar OR VECTOR then i had to adapt the code for that. I am having issues picking each element from vector x.

My code so far
function y=sfun(x,a,n)
x=input('enter "x" as a vector [a b] or variable: ');
n=input('enter "n" parameter: ');
a=input('enter "a" parameter: ');
k=length(x);
for z=x(1:k)
if z>a
y=(z-a).^n;
else
y=0;
end
end


I get 27. Which is just the correct answer for 5. When x=0 it should be giving me 0 obviously which it is not.

Added attachment of the piecewise function I am trying to make.


Attachment:singfunc.PNG (413660 bytes | downloaded 7 times)