I have tried solving DFT but i am getting an error

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Sam17
Sam17 2017-9-20
评论： Walter Roberson 2017-9-20
Here is my code: i tried solving using matrix multiplication
f1=7;f2=21;
fs=220; %Sampling frequency f2*10
ts=1/fs; %sampling time
t=0:10-ts;
y=sin(2*pi*t*f1)+sin(2*pi*t*f2); %given data set
N=length(y);
n = 0:1:N-1; % row vector for n
k = 0:1:N-1; % row vecor for k
WN = exp(-1j*2*pi/N); % the w elements
n1= transpose(n);
nk = n1*k; % creates a N by N matrix of nk values
WNnk = WN .^ nk; % DFT matrix
Xk = WNnk.*y;
plot(n,xk)
Here is my error message:
Error using .* Matrix dimensions must agree.
Error in a21 (line 13) Xk = WNnk.*y;
Please help me plot:
  1 个评论
Walter Roberson
Walter Roberson 2017-9-20
At the time of your line WNnk.*y then WNnk is 10 x 10 and y is 1 x 10. What size of output were you expecting from that?
Note: your line
t=0:10-ts;
should be
t=0:ts:10-ts;

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