Hi Jayasree,
The issue that you are facing currently is your obejctive function seems to be set up for low-pass filter.
Your current expression for (h):
h(i) = 1-(cos(wc * (M/2)) - 1i * sin(wc * (M/2)));
This above uses a fixed angle, resulting in same values of h(i) which could be why your original filter response was not shaping properly.
To modify it for a high-pass filter, you can adjust the desired response (h) and the way you compute the error (e1). Please refer to following implementation:
function [o] = objFunction(x)
M = 10;
wc = 0.5 * pi;
hr = 0;
h = zeros(1, M/2);
% Calculate the actual filter response hr
for i = 1:(M/2)
hr = hr + 2 * x(i) * cos(wc * ((M/2) - i));
end
hr = hr + x(M/2);
% Desired high-pass filter response
for i = 1:(M/2)
h(i) = -1 * (cos(wc * ((M/2) - i)) - 1i * sin(wc * ((M/2) - i)));
end
% Error between desired and actual response
e1 = abs(hr - h);
o = sum(e1);
end
Please note, for error calculation, you can also use the MSE(Mean Squared Error) as an alternative to absolute error.
Hope this helps
