Why am I getting this error "??? error using ==> times matrix dimensions must agree" in matlab?

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design a FIR low pass filter using Kaiser window
a1phap=0.1
a1phas=44
ws=30
wp=20
wsf=100
B=ws-wp
wc=0.5*(ws+wp)
wcr=wc*2*pi/wsf
D=(a1phas-7.95)/14.36
N=ceil((wsf*D/B)+1)
a1pha=(N-1)/2
gamma=(.5842*(a1phas-21).^(0.4)+0.07886*(a1phas-21))
n=0:1:N-1
hd=sin(wcr*(n-a1pha))./(pi*(n-a1pha))
hd(a1pha+1)=0.5
wk=(kaiser(N,gamma))
hn=hd.*wk % *(HERE I AM GETTING THIS ERROR)*
W=85:5:120
h=freqz(hn,1,W)
plot(W/pi,20*log10(abs(h)))
those two matrices have the same dimensions of 27..still why this error?

Accepted Answer

Cedric
Cedric on 21 Apr 2013
You have to transpose either wk or hd, because one is a column vector and the other a row vector. E.g.
hn = hd .* wk.'

More Answers (2)

the cyclist
the cyclist on 21 Apr 2013
Edited: the cyclist on 21 Apr 2013
I don't have the Signal Processing Toolbox, so I can't execute the kaiser() function. However, the documentation indicates that it will output a column vector. Your vector hd is a row vector, so it does not actually have the same dimension. You need to transpose one of them.

Chandra Shekhar
Chandra Shekhar on 21 Apr 2013
Edited: Chandra Shekhar on 21 Apr 2013
Don't use dot product,edit that line like this
hn=hd*wk;
but you will get single value after multiplying,but 'freqz' function requires vector as a input.
if you need vector then do like this, you will get waveform.
hn=hd. * wk ' ;

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