Linear scale to Log scale in CWT

Following this code..

>> y=[zeros(1,500) ones(1,500)];
>> cwt(y,1:128,'haar','plot');
>> colormap jet
>> colorbar

Here the plot is showing linear scale..

How to convert the linear scale to show log scale in CWT command..

I tried with this code

>>cwt(y,log10(1:128),'haar','plot');

But wavelet doesn't scale '0' scale so giving error like

    **************************************
  ERROR ... 
  --------------------------------------
   cwt ---> Invalid Value for Scales !
  **************************************

??? Error using ==> cwt at 74
Invalid Value for Scales !

So what is the solution to my problem ( conversion of linear to log scale ) ?

[Daniella Della-Giustina]

Did you ever find a solution?

Answer 1

[Robert U]

Hi Raviteja,

the command cwt() allows to use the output matrix of the wavelet transform to produce your own plots. One possibility is to use the following way:

% attention: this is the 'old' command call, since version 2016b there is a 'new' command call
% assumption - the sampling frequency is 500 Hz
[wt,f] = cwt(y,1:128,'haar',500);

% create figure and axes
fh = figure;
ah = axes(fh);
% plot the absolute value of wavelet transform matrix (frequency vector may not contain '0 Hz'
imagesc(ah,1:size(wt,2),f,abs(wt))
colormap(fh,'pink')    % change colormap to 'pink' to reproduce 'cwt'-look
ah.XScale = 'log';     % change scale of x axis to logarithmic

You can change almost all figure related parameters in that manner.

Kind regards,

Robert