using knnsearch for QPSK demodulation

rec_syms = knnsearch([real(symbol_book) imag(symbol_book)], [real(X_hat) imag(X_hat)]) - 1;

I get this error:

Error using KDTreeSearcher/knnsearch (line 74) Y must be a matrix with 8 columns.
Error in knnsearch (line 142) idx = knnsearch(O,Y,'k',numNN, 'includeties', includeTies);
Error in OFDM_image (line 139) rec_syms = knnsearch([real(symbol_book) imag(symbol_book)], [real(X_hat) imag(X_hat)]) - 1;

symbol_book is 1x4 matrix which has the QPSK reference quadrants

{0.7071+0.7071i, -0.7071+0.7071i, -0.7071-0.7071i, 0.7071-0.7071i}.

Now, the x_hat is the estimated data with 50000x1 matrix. What i am trying to do is find the min distance between the QPSK reference and the actual received data. Not sure if maybe when i switched to 2015 matlab would have an effect! please advise

[Ray]

Thanks for your response. symbol_book is 1x4 matrix which has the QPSK reference quadrants {0.7071+0.7071i, -0.7071+0.7071i, -0.7071-0.7071i, 0.7071-0.7071i}. Now, the x_hat is the estimated data with 50000x1 matrix. What i am trying to do is find the min distance between the QPSK reference and the actual received data. Not sure if maybe when i switched to 2015 matlab would have an effect! please advise

[Walter Roberson]

Duplicates http://uk.mathworks.com/matlabcentral/answers/258973-i-get-an-error-in-knnsearch