How can i regexp this sample text?

im looking to grab all the data after "CHANNEL" into a cell array such that C{1,1} = Shell Angle and so on

and looking to grab all the data after "UNITS" into a separate cell array such that D{1:1} = deg and so on

Im having trouble with the non alphanumeric stuff such as @, (, ), etc

Any help greatly appreciated, Thanks!

Answer 1

[Stephen23]

Here is a regexp-based solution which does NOT use hard-coded variable names (it automatically detects the variable names), and does NOT magically create variables in the MATLAB workspace... read this to know why dynamically naming variables is a bad way to write code:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

The code is quite straighforward: the first regexp identifies the variable name and square bracket pairs, the second regexp identifies the list values themselves:

str = fileread('sample2.txt');
tkn = regexp(str,'(\w+)\s+=\s+\[([^\]]+)\]','tokens');
tkn = vertcat(tkn{:});
hdr = tkn(:,1);
tkn = regexp(tkn(:,2),'''([^'']+)''','tokens');
tkn = cellfun(@(c)[c{:}],tkn,'uni',0);

And checking:

>> hdr{2}
ans =
UNIT
>> tkn{2}
ans = 
  Columns 1 through 8
    'deg'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'
  Columns 9 through 16
    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'
  Columns 17 through 20
    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'

You can access the data directly from the cell arrays, or use them to define a convenient structure:

>> S = cell2struct(tkn,hdr,1);
>> S.UNIT
ans = 
  Columns 1 through 8
    'deg'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'
  Columns 9 through 16
    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'
  Columns 17 through 20
    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'    'lbf/(ft.s)'
>> S.CHANNEL
ans = 
  Columns 1 through 8
    'Shell Angle'    [1x30 char]    [1x30 char]    [1x30 char]    [1x30 char]    [1x30 char]    [1x30 char]    [1x30 char]
  Columns 9 through 16
    [1x30 char]    [1x30 char]    [1x31 char]    [1x31 char]    [1x31 char]    [1x31 char]    [1x31 char]    [1x31 char]
  Columns 17 through 20
    [1x31 char]    [1x31 char]    [1x31 char]    [1x31 char]

[Adam Danz]

+1

@Tyler , I'd go for this strategy rather than my literal interpretation of your goals.

[Guillaume]

As well as cell array and structure, you could also use a Map:

>> map = containers.Map(hdr, tkn);
>> map('UNIT')
ans =
  1×20 cell array
  Columns 1 through 3
    {'deg'}    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}
  Columns 4 through 6
    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}
  Columns 7 through 9
    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}
  Columns 10 through 12
    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}
  Columns 13 through 15
    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}
  Columns 16 through 18
    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}
  Columns 19 through 20
    {'lbf/(ft.s)'}    {'lbf/(ft.s)'}

Whatever you do, do not use values coming out of a text file to name actual variables. Creating variables dynamically is a sure way to have bugs, you may well overwrite an existing variable if for some reason the input file is slightly different.

Answer 2

[Adam Danz]

In this solution, the file is first read into matlab as a char array. Then I segregate the "CHANNEL" variable and convert it into Matlab syntax so it can be converted to a cell array. The same is then done with the "UNIT" variable.

file = 'C:\Users\name\Documents\MATLAB\sample2.txt'; 
c = fileread(file);
% segregate "Channel" array
chanTxt = regexp(c,'CHANNEL.+?\]', 'match');
% Replace ampersands with elipses
chanTxt = strrep(chanTxt, '&', '...');
% Replace square bracket with curly brackets
chanTxt = strrep(chanTxt, '[', '{');
chanTxt = strrep(chanTxt, ']', '}');
% Execute string to convert it to cell array of strings
eval(chanTxt{:}); % Now you have a variable named "CHANNEL"
%  CHANNEL'  % (first 5 lines)
% ans =
%   20×1 cell array
%     {'Shell Angle'                    }
%     {'Surface Heat Flux @ GridLine=1' }
%     {'Surface Heat Flux @ GridLine=2' }
%     {'Surface Heat Flux @ GridLine=3' }
%     {'Surface Heat Flux @ GridLine=4' }
%     {'Surface Heat Flux @ GridLine=5' }

% Now go through the same process for "UNIT"
unitTxt = regexp(c,'UNIT.+?\]', 'match');
unitTxt = strrep(unitTxt, '&', '...');
unitTxt = strrep(unitTxt, '[', '{');
unitTxt = strrep(unitTxt, ']', '}');
eval(unitTxt{:}); % Now you have a variable named "UNIT"

A great work station to develop regular expressions: https://regex101.com/