MATLAB - Read Textfile (lines with different formats) line by line - matlab

Question

I have a text file (lets call it an input file) of this type:
%My kind of input file % Comment 1 % Comment 2
4 %Parameter F
2.745 5.222 4.888 1.234 %Parameter X
273.15 373.15 1 %Temperature Initial/Final/Step
3.5 %Parameter Y
%Matrix A
1.1 1.3 1 1.05
2.0 1.5 3.1 2.1
1.3 1.2 1.5 1.6
1.3 2.2 1.7 1.4
I need to read this file and save the values as variables or even better as part of different arrays. For example by reading I should obtain Array1.F=4; then Array1.X should be a vector of 3 real numbers, Array2.Y=3.5 then Array2.A is a matrix FxF. There are tons of functions to read from text file but I don't know how to read these kind of different formats. I've used in the past fgetl/fgets to read lines but it reads as strings, I've used fscanf but it reads the whole text file as if it is formatted all equally. However I need something to read sequentially with predefined formats. I can easily do this with fortran reading line by line because read has a format statement. What is the equivalent in MATLAB?

Answer 1

This actually parses the file you posted in your example. I could've done better, but I'm tired today:
res = struct();
fid = fopen('test.txt','r');
read_mat = false;
while (~feof(fid))
% Read text line by line...
line = strtrim(fgets(fid));
if (isempty(line))
continue;
end
if (read_mat) % If I'm reading the final matrix...
% I use a regex to capture the values...
mat_line = regexp(line,'(-?(?:\d*\.)?\d+)+','tokens');
% If the regex succeeds I insert the values in the matrix...
if (~isempty(mat_line))
res.A = [res.A; str2double([mat_line{:}])];
continue;
end
else % If I'm not reading the final matrix...
% I use a regex to check if the line matches F and Y parameters...
param_single = regexp(line,'^(-?(?:\d*\.)?\d+) %Parameter (F|Y)$','tokens');
% If the regex succeeds I assign the values...
if (~isempty(param_single))
param_single = param_single{1};
res.(param_single{2}) = str2double(param_single{1});
continue;
end
% I use a regex to check if the line matches X parameters...
param_x = regexp(line,'^((?:-?(?:\d*\.)?\d+ ){4})%Parameter X$','tokens');
% If the regex succeeds I assign the values...
if (~isempty(param_x))
param_x = param_x{1};
res.X = str2double(strsplit(strtrim(param_x{1}),' '));
continue;
end
% If the line indicates that the matrix starts I set my loop so that it reads the final matrix...
if (strcmp(line,'%Matrix A'))
res.A = [];
read_mat = true;
continue;
end
end
end
fclose(fid);