Home > chronux > spectral_analysis > continuous > quadcof.m

## PURPOSE Helper function to calculate the nonstationary quadratic inverse matrix

## DESCRIPTION ``` Helper function to calculate the nonstationary quadratic inverse matrix
N             (number of samples)
NW: Time bandwidth product
order: order (number of coefficients, upto 4NW)

Outputs:

sumV: sum of the quadratic inverse eigenvectors```

## CROSS-REFERENCE INFORMATION This function calls:
This function is called by:

## SOURCE CODE ```0001 function [A,sumV] = quadcof(N,NW,order)
0002 % Helper function to calculate the nonstationary quadratic inverse matrix
0003 % Usage: [A,sumV] = quadcof(N,NW,order)
0004 % N             (number of samples)
0005 % NW: Time bandwidth product
0006 % order: order (number of coefficients, upto 4NW)
0007 %
0008 % Outputs:
0009 %
0010 % A: quadratic inverse coefficient matrix
0011 % sumV: sum of the quadratic inverse eigenvectors
0012
0013 A = zeros(2*NW,2*NW,order);
0015 [P,alpha] = dpss(N,NW,'calc');
0016
0017 for ii = 1:order
0018
0019   for jj = 1:2*NW
0020     for kk = 1:2*NW
0021     A(jj,kk,ii) = sqrt(alpha(jj)*alpha(kk))*...
0022                       sum(P(:,jj).*P(:,kk).*V(:,ii));
0023     end;
0024   end;
0025 end;
0026 sumV=sum(V)/N;
0027
0028```

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