MATLAB: Read file with non-uniform lines

blockblocksformatspecMATLABtextscan

Hi. I'm a Matlab newbie. I would like to read in a file where the lines have different formats, as below.
% Coordinates
%   Code    ID      X         Y
    C       101     0.001     0.001
    C       102     1.002     0.002
    C       103     1.003     1.003
    C       104     0.004     1.004
% Distances
%   Code    ID      From      To      Dist
    D       201     101       103     1.417
    D       202     102       104     1.414
If the first character is C, use…
A = textscan(fid,'%c %d %f %f')
If the first character is D, use…
A = textscan(fid,'%c %d %d %d %f')
After, I'd like to assign the data to structs (c.id, c.x, c.y, d.id, d.from, d.to, d.dist), but first I think I just need to get it scanned in. Is it possible to apply some logic to reading the file? Thank you.

Best Answer

Named tokens, I said. Do not extract the lines ahead of time.
FileText = fileread(YourFileName);
Ctokens = regexp(FileText, '^\s*C\s+(?<ID>\d+)\s+(?<X>\S+)\s+(?<Y>\S+)', 'names', 'lineanchors');
%Ctokens will now be a struct array with field names ID, X, and Y, each of which are character vectors.
C.ID = str2double({Ctokens.ID});
C.X = str2double({Ctokens.X});
C.Y = str2double({Ctokens.Y});
Dtokens = regexp(FileText, '^\s*D\s+(?<ID>\d+)\s+(?<From>\d+)\s+(?<To>\d+)\s+(?<Dist>\S+)', 'names', 'lineanchors');
%Dtokens will now be a struct array with field names ID, From, To, Dist, each of which are character vectors.
D.ID = str2double({Dtokens.ID});
D.From = str2double({Dtokens.From});
D.To = str2double({Dtokens.To});
D.Dist = str2double({Dtokens.Dist});
Amount of processing work is pretty minimial. Pretty much all of the effort is in figuring out the proper regexp patterns to use (which can be pretty tricky when there are variant lines.)
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