CONSTRUCTPHASE - Construct phase for DGT

Usage

c=constructphase(s,g,a);
c=constructphase(s,g,a,tol);
c=constructphase(c,g,a,tol,mask);
c=constructphase(c,g,a,tol,mask,usephase);
[c,newphase,usedmask,tgrad,fgrad] = constructphase(...);

Input parameters

Output parameters

Description

constructphase(s,g,a) will construct a suitable phase for the postive valued coefficients s.

If s is the absolute values of the Gabor coefficients of a signal obtained using the window g and time-shift a, i.e.:

c=dgt(f,g,a,M); s=abs(c);

then constuctphase(s,g,a) will attempt to reconstruct c.

The window g must be Gaussian, i.e. g must have the value 'gauss' or be a cell array {'gauss',tfr}.

constructphase(s,g,a,tol) does as above, but sets the phase of coefficients less than tol to random values. By default, tol has the value 1e-10.

constructphase(c,g,a,M,tol,mask) accepts real or complex valued c and real valued mask of the same size. Values in mask which can be converted to logical true (anything other than 0) determine coefficients with known phase which is used in the output. Only the phase of remaining coefficients (for which mask==0) is computed.

constructphasereal(c,g,a,M,tol,mask,usephase) does the same as before but uses the known phase values from usephase rather than from c.

In addition, tol can be a vector containing decreasing values. In that case, the algorithm is run numel(tol) times, initialized with the result from the previous step in the 2nd and the further steps.

Further, the function accepts the following flags:

'freqinv' The constructed phase complies with the frequency

invariant phase convention such that it can be directly used in idgtreal. This is the default.

'timeinv' The constructed phase complies with the time-invariant

phase convention. The same flag must be used in the other functions e.g. idgtreal

This function requires a computational subroutine that is only available in C. Use ltfatmex to compile it.