using regexp for space delimited strings in text file.

I need to extract repeated strings' lines from the attached text file. For example there are 2 lines which start with "P 1" (two spaces after P) string in the data file. I need to extract 2nd and 4th column of these lines as follows;

array_P1=[ 6444.951599 -24080.372159 -8934.980576; 6645.371003 -22892.293251 -11497.619680];

I use following codes (from Stephen Cobeldick) if there are no space in repeated strings (for example P1);

fid = fopen('data_file.txt','rt');
str = fscanf(fid,'%c',Inf);
fclose(fid);
C = regexp(str,'^P1( +\S+)+\s+$','lineanchors','tokens');
C = regexp(vertcat(C{:}),'\S+','match');
N = str2double(vertcat(C{:}));

But this doesn't work if there are spaces in the repeated strings as in my example (P 1)

Answer 1

[Stephen23]

Try this:

% textscan options:
opt = {'MultipleDelimsAsOne',true,'CollectOutput',true};
% required arrays:
str = 'X';
dtv = [];
dat = {};
% open textfile:
fid = fopen('data.txt','rt');
while ischar(str)
    % skip lines until first char is '*' (date vector):
    while ~strcmp(str(1),'*')
        str = fgetl(fid);
    end
    % convert date vector to numeric:
    dtv(end+1,:) =  str2double(regexp(str(2:end),'\S+','match')); %#ok<SAGROW>
    % get file position:
    pos = ftell(fid);
    % read first line of matrix:
    str = fgetl(fid);
    if ischar(str)
        % calculate how many columns in the matrix:
        N = numel(regexp(str(5:end),'\S+','match'));
        fmt = repmat('%f',1,N);
        % rewind one line:
        fseek(fid,pos,'bof');
        % read entire matrix:
        dat{end+1} = textscan(fid,['%4[^*]',fmt],opt{:}); %#ok<SAGROW>
    end
end
% concatenate data in cell arrays:
dat = vertcat(dat{:});
mat = vertcat(dat{:,2});

This reads the entire data matrix (between the date vectors) into a numeric matrix inside the cell array dat, and the date vectors in dtv. It automatically adjusts for the different numbers of columns in your matrices. Some important assumptions:

• the first columns comprise of exactly four characters (which may be spaces).
• the date vectors always start with asterisks, but no other lines do.
• no empty lines between the date vectors and the data matrices.
• the matrices contain numeric data only.

Have a look inside dat, and pick the data that you need:

>> cell2mat(cellfun(@(m)m(1,[1,2,3]),dat(:,2),'UniformOutput',false))
ans =
   1.0e+04 *
    0.6445   -2.4080   -0.8935
    0.6645   -2.2892   -1.1498

I also concatenated the matrices into mat, which lets gives you all of the matrices in one. This might be easier to access:

>> mat([1,10],[1,2,3])
ans =
   1.0e+04 *
    0.6445   -2.4080   -0.8935
    0.6645   -2.2892   -1.1498

I tested this code on both of the files that you have provided (this question, and your last question), which are also available here:

[sermet]

thank you Stephen, I always really appreciate your help.

Answer 2

[Guillaume]

Well, I guess it's time for you to learn the regular expression language.

This regex should work for you:

'^P\s*1( +\S+)+\s+$'

It simply adds 0 or more (the *) whitespace characters (the \s) between P and 1.

[sermet]

I modified the code as you explained;

C = regexp(str,'^P\s*1( +\S+)+\s+$','lineanchors','tokens')

But it produced empty C

{}