MF_autocorr MD_autocorr ME_autocorr
 Function Spatial autocorrelation function
 Syntax C/C++ #include void MF_autocorr( fMatrix Y, fMatrix X, ui ht, ui len ); C++ MatObj #include void matrix::autocorr( const matrix& MX); Pascal/Delphi uses MFstd; procedure MF_autocorr( MY, MX:fMatrix; ht, len:UIntSize );
 CUDA function C/C++ #include int cudaMF_autocorr( fMatrix d_Y, fMatrix d_X, ui ht, ui len ); void MFcu_autocorr( fMatrix h_Y, fMatrix h_X, ui ht, ui len ); CUDA function Pascal/Delphi uses MFstd; function cudaMF_autocorr( d_MY, d_MX:fMatrix; ht, len:UIntSize ): IntBool; procedure MFcu_autocorr( h_MY, h_MX:fMatrix; ht, len:UIntSize );
 Description The spatial autocorrelation function (SACF) of MX is calculated and stored in MY in wrap-around order in both dimensions: The row elements MYi,0 to MYi,len/2-1 contain the SACF for zero and positive x lags. Beginning with the most negative lag in MYi,len/2+1, the elements up to MYi,len-1 contain the SACF for negative lags. Since this function assumes MX to be periodic, the SACF for the most positive lag is identical to the SACF for the most negative lag. This element is stored as Yi,len/2. Similarly, the column elements MY0,j to MYlen/2-1,j contain the SACF for zero and positive y lags. Beginning with the most negative lag in MYlen/2+1,j, the elements up to MYlen-1,j contain the SACF for negative lags. To get the SACF into normal order, you may call MF_Rows_rotate( MY, ht, len, len/2 ); MF_Cols_rotate( MY, ht, len, ht/2 ); After that, the zero point is at the position MYht/2,len/2. In case MX is non-periodic, you should avoid end effects by the methods described in connection with MF_convolve. Both ht and len must be integer powers of 2. About special versions with the prefixes MFl_ and MFs_, consult chapter 4.8 of http://www.optivec.com/vecfuncs/.
 Error handling If either len or ht is not a power of 2, VF_FFT (on which MF_autocorr is based) complains "Size must be an integer power of 2" and the program is aborted.
 See also MF_FFT,   MF_convolve,   VF_autocorr,   chapter 12