How do I correct an error about matrix dimensions. The error appears in line 10.

m=1;
D=0.5;
lambda=20;
K=(2*pi)/lambda;
z=0:10:1000;
C=2./(m.*pi).*sin(m.*pi.*D);

d=0;
for i=1:length(z)
d=d+C(i)*exp(-1i.*K.*z);
end
g=sign(d);
k=20001;
rect=zeros(1,k);
for n=1:k
    if x(n)>0&x(n)<1
    rect(n)=1;
    elseif x(n)==0||x(n)==1
    rect(n)=0.5;
    else
    rect(n)=0;
end
n=n+1;
end
hz=rect.*g;
re=real(g);
Y=fftshift(fft(g))/length(g);
%plot(z,abs(Y))
plot(z,hz)
%plot(z,g)

[Rik]

d=d+C(i)*exp(-1i.*K.*z); is not a valid syntax, use d=d+C(i)*exp(-1*i.*K.*z); instead. Also, you are calling C(i), but C is only a scalar.

[Image Analyst]

d=d+C(i)*exp(-1i.*K.*z) IS valid syntax. -1i is how you use the imaginary variable i:

>> z=exp(-1i*2)
z =
         -0.416146836547142 -     0.909297426825682i

Works fine. Using -1 * i is a totally different operation than using -1i, but they both work.