Skill with regexprep?

I am new to MATLAB but have years of experience in Perl.

Can anyone offer suggestions as to how to improve the following MATLAB code?

Although what I have works, are there better ways to loop over the record to get closer to the one-line construction of Perl?

My thanks, in advance, for advice and tutorials!

The requirement is to replace all occurrences of a repeat construction "N*Value" with N repeats of the Value. This is part of the import routine for existing data files.

A Perl construction can do this in a single line. In Perl: s!(\d+)\*(\S+)!"$2 " x $1!ge;

An example data record:

DXV

30*60 30*40 30*20 30*10 30*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 10*5

3 2 1 0.5 0.3 0.15 0.08 0.04 0.02 5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3

30*5 30*10 30*20 30*40 30*60

/

My current code in MATLAB works OK, but is much clumsier:

    record=join(file);
    [startIndex,endIndex]=regexp(record,'(\d+)\*(\S+)');
    if(~isempty(startIndex))
        for n=numel(startIndex):-1:1
            tokenNames=regexp(extractBetween(record,startIndex(n),endIndex(n)),'(?<count>\d+)\*(?<value>\S+)','names');
            x_record=strings(str2double(tokenNames.count),1);
            x_record(:)=tokenNames.value;
            record=replaceBetween(record,startIndex(n),endIndex(n),join(x_record));
        end
    end

[the cyclist]

Can you upload a MAT file with the data record, so that we can experiment without needing to guess exactly how it is stored?

[Mike]

Ah. Didn't know that I could do that. Is the attached what you'd need?

I saved the workspace from within the function after removing extraneous material. Input is file (and key). Output is record. The extra two lines at the end of the code to complete the formatting of the record are:

record=split(record);

record=record(1:end-1);

Again, my thanks!

Answer 1

[Stephen23]

This should get you started:

>> str = '5*0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 30*5 30*10 30*20 30*40 30*60';
>> fun = @(n,c)repmat(sprintf(' %s',c),1,str2double(n)); % or JOIN rather than SPRINTF.
>> str = regexprep(str,'\s*(\d+)\*(\S+)','${fun($1,$2)}')
str =
 0.02 0.02 0.02 0.02 0.02 0.02 0.04 0.08 0.15 0.3 0.5 1 2 3 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60

https://www.mathworks.com/help/matlab/matlab_prog/dynamic-regular-expressions.html

If you use join then you can get rid of the leading \s*.

[Mike]

Thanks for the rapid assist, and the link.

Mike