CODEWITHSUNDEEP
matlab
Artur Castiel
Artur Castiel

Reputation: 185

Read multiple data from a MATLAB file

I am currently trying to read data from a text file written exactly like this:

Height = 10
Length = 10
NodeX = 11
NodeY = 11
K = 10

I've written a small code like this

fileID = fopen('input.dat','r');
[a, b] = fscanf(fileID, '%s %f')

And I get the following answer:

a =

    72
   101
   105
   103
   104
   116


b =

     1

It seems quite obvious I am not mananging to specify the format specification. I would like to know how to pick a string along with a float multiple times in the same file.

Upvotes: 1

Views: 139

Answers (2)

sco1
sco1

Reputation: 12214

As the documentation for fscanf states:

If formatSpec contains a combination of numeric and character specifiers, then fscanf converts each character to its numeric equivalent. This conversion occurs even when the format explicitly skips all numeric values (for example, formatSpec is '%*d %s').

MATLAB can be annoyingly bad at reading mixed data types. One possible alternative is to read each line and split up your data using a simple regular expression:

fileID = fopen('results.txt','r');

mydata = {};
ii = 1;
while ~feof(fileID) % While we're not at the end of the file
    tline = fgetl(fileID); % Get next line
    mydata(ii,:) = regexp(tline, '([a-zA-Z])* = (\d*)', 'tokens');
    ii = ii + 1;
end

fclose(fileID);

This returns a 5 x 1 cell array where each cell contains 2 cells (slightly annoying, but you can pull them out) that match your data. In this case, mydata{1}{1} is Height and mydata{1}{2} is 10.

Edit:

And you can flatten your cell array with a reshape call:

mydata = reshape([mydata{:}], 2, [])';

Which turns mydata in this case into a 5x2 cell array.

Upvotes: 2

hbaderts
hbaderts

Reputation: 14371

The fscanf function is a low-level I/O function and is often not the best choice for such rather high-level file input. One alternative would be to use the textscan function, which allows quite advanced format specifications:

fileID = fopen('input.dat','r');
C = textscan(fileID,'%s = %d')

which creates a 1x2 cell array. The first cell C{1} contains another 5x1 cell, where each field contains the name of the field, e.g. 'Height'. The second cell C{2} contains a 5x1 vector containing all integer values from the file.

Upvotes: 2

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