Matlab:Reading textfile into matrix

Question

I want to read data from a text file in Matlab. The file describes a surface consists of two parts: 1)A header with information on x,y dimensions in pixels and nm etc. 2)Matrix with height values (512x512)

When I try to read just the matrix first I end up with a single column vector instead of a matrix C = textscan(id,'%f','HeaderLines',18,'Delimiter','\t') The file contains " " seperated values and the lines seperated the rows of the matrix. It works when I manually delete the header and read it with A=dlmread(path,'\t',[0 0 511 511]);

I want to obtain the same 512x512 matrix with textscan so that I can later also parse the header - how can I do that?

anandr anandr · Accepted Answer · 2014-08-18T17:58:00

If you are not strictly bound to textscan, you may use fscanf instead (see docs). Like this:

fid = fopen('FileName.txt');

% here you have to skip (or parse) your header lines
% and determine number of rows/columns in your data matrix

A = fscanf(fid, '%g', [NColumns NRows]);
fclose(fid);

% Transpose so that A matches
% the orientation of the file
A = A';

UPDATE1

This code might be not very elegant, but it will parse your header into FileInfo structure so you may use the data later in your code.

% sample file header
%
% # File Format = ASCII
% # Created by SPIP 6.2.8.0 2014-08-15 20:41
% # Original file: D:\...
% # x-pixels = 512
% # y-pixels = 512
% # x-length = 319375
% # y-length = 319375
% # x-offset = 0
% # y-offset = 0
% # z-unit = [nm]
% # scanspeed = 638.75
% # forcecurve = 0
% # voidpixels =76
% # description =62:Confocal Height Image  Date: 2013-08-20T13:36 User: Unknown
% # Start of Data: MATRIX

fid = fopen('text.txt','r');

FileInfo  = [];
tmpString = '';   % initializing the s
while isempty(strfind(tmpString,'Start of Data: MATRIX'))

    % we read a string from file
    tmpString = fgetl(fid);
    % and split it into left and right parts according to the '=' position
    [kev,val] = strtok( tmpString(3:end) , ':=' );

    % remove spaces from key name and make it a valid variable name in MatLab
    keyName = genvarname( strrep(strrep(kev,'-',''),' ','') );

    % check if key value is a number
    [x,OK]    = str2num(strtrim(val(2:end)));

    % if value is a number, use it otherwise leave the trimmed original string
    if OK
        FileInfo.(keyName) = x;
    else
        FileInfo.(keyName) = strtrim(val(2:end));
    end

end

% Now we can read the data
A = fscanf(fid, '%g', [FileInfo.xpixels FileInfo.ypixels]);
fclose(fid);

% Transpose so that A matches
% the orientation of the file
%A = A';

Matlab:Reading textfile into matrix

1 Answers