Unexpected separate output of exchange() function

[katarkon]

It should be expected that separate output of the function returns a set of the spectra with single line for each. But exchange() function in slow rate limit returns some spectra with several lines. Is any way to rid it out?

[Stefan Stoll]

Looking at the code of exchange, it can be seen that each spectrum is the sum over all the sites of a particular line:

Code: Select all

    for iLine=1:nLines
      spc_ = 0;
      for iSite=1:nSites
        % Calculation of spc_
      end
      if separateOutput
        spc(iLine,:) = spc_;
      else
        spc = spc + spc_;
      end
    end

You will have to modify this to store the spectra separately not only for each line (iLine) but also for each site (iSite). Something along the lines of the following should work:

Code: Select all

    % code within Opt.Method = 2 branch of switch statement
    idx = 1;
    for iLine=1:nLines
      for iSite=1:nSites
        % Calculation of spc_
        if separateOutput
          spc(idx,:) = spc_;
          idx = idx + 1; 
        else
          spc = spc + spc_;
        end
      end
    end

It might be necessary to adjust some other spots in the code as well.

[katarkon]

Yes, this idea should be working, although there are some problems with such 'hyperseparated' output.
Firstly, some zero spectra are generated. Surprisingly, in the case of fast exchange a pair of zero spectrum and line spectrum is generated instead of expected pair of equal spectra. Of course, the zero spectra may be easily detected and discarded However Opt.reduce parameter should be 0 for fast exchange and 1 for slow one to get the predictable results. More sadly, the removing of the duplicates works only for two-site mutual exchange (although its algorythm looks adoptable for more general cases).
Secondly, if nuclei with I>1/2 are used, the order of the spectra becomes unpredictable. I propose that the 'brute force' code will be working:

Code: Select all

    idx = 1;
    for iLine=1:nLines
      for iSite=1:nSites
        % Calculation of spc_
        if separateOutput
          spc(idx,:) = spc_;
          [~,B0] = max(spc_); %approximate resonance position
          spc(idx,nPoints+1)=B0; %indexing the spectra by resonance position
          idx = idx + 1;
        else
          spc = spc + spc_;
        end
      end
      if separateOutput
      spc=sortrows(spc,nPoints+1); %sorting
      spc(:,nPoints+1)=[]; %removing indexes
      end
    end