xo=largestr(x,p); xo=largestr(x,p,mtype); [xo,N]=largestr(...);
largestr(x,p) returns an array of the same size as x keeping the fraction p of the coefficients. The coefficients with the largest magnitude are kept.
[xo,n]=largestr(xi,p) additionally returns the number of coefficients kept.
Note: If the function is used on coefficients coming from a redundant transform or from a transform where the input signal was padded, the coefficient array will be larger than the original input signal. Therefore, the number of coefficients kept might be higher than expected.
largestr takes the following flags at the end of the line of input arguments:
| 'hard' | Perform hard thresholding. This is the default. |
| 'wiener' | Perform empirical Wiener shrinkage. This is in between soft and hard thresholding. |
| 'soft' | Perform soft thresholding. |
| 'full' | Returns the output as a full matrix. This is the default. |
| 'sparse' | Returns the output as a sparse matrix. |
Note: If soft- or Wiener thresholding is selected, one less coefficient will actually be returned. This is caused by that coefficient being set to zero.
S. Mallat. A wavelet tour of signal processing. Academic Press, San Diego, CA, 1998.