MATLAB: Accessing data from a file and putting it into a matrix in Matlab, plus headers.

accessing dataheadersmatrix

I am trying to read data in from a .svc file, which consists of 7 columns and 212 rows. I have managed to read it in by doing:
>>fid = fopen('u001_s01_sign_ds2-tb-0c_01.svc','r');
>>data = textscan(fid,'%f %f %f %f %f %f %f','HeaderLines',1);
>>fclose(fid);
I found it difficult to understand how to read data straight into a matrix, using dlmread, so have tried to go around using that, as above.
To store the data into a matrix after reading it in I used:
>>A=[data{1} data{2} data{3} data{4} data{5} data{6} data{7}]
Now I want to add headers to each column, but I am not sure how to go about that. I have found the following code, that looks like it will do what I need, but I do not understand it:
function writeWithHeader(fname,header,data)
% Write data with headers
% fname: filename
% header: cell of row titles
% data: matrix of data
f = fopen(fname,'w');
%Write the header:
fprintf(f,'%-10s\t',header{1:end-1}); fprintf(f,'%-10s\n',header{end});
%Write the data: for m = 1:size(data,1)
    fprintf(f,'%-10.4f\t',data(m,1:end-1));
    fprintf(f,'%-10.4f\n',data(m,end));
end
fclose(f);
This code was from http://stackoverflow.com/questions/7081721/adding-a-header-to-a-matrix-in-matlab . The comment to go with this was, ‘You just need to play with the fprintf format string…’. I have saved the code into a function in Matlab, saving it as writeWithHeader.m, and I understand that to run the function I type into the Matlab command window:
>> writeWithHeader('u001_s01_sign_ds2-tb-0c_01.svc', X Y Z A B C D, A)
Where X Y Z A B C D are my header names, and A is the matrix of data I want the headers added to. Is this correct? Is there maybe a better of doing all this?

Best Answer

Is this correct? Basically, yes. When you call the function, header should be a cell array of strings, so
writeWithHeader('u001_s01_sign_ds2-tb-0c_01.svc', {'X' 'Y' 'Z' 'A' 'B' 'C' 'D'}, A)
Also, FWIW, I'd simplify the function to this:
function writeWithHeader(fname,header,data)
% Write data with headers
% fname: filename
% header: cell of row titles
% data: matrix of data
f = fopen(fname,'w');
%Write the header:
n = length(header);
fmt = [repmat('%-10s\t',1,n-1),'%-10s\n'];
fprintf(f,fmt,header{:});
%Write the data:
fmt = [repmat('%-10.4f\t',1,n-1),'%-10.4f\n'];
fprintf(f,fmt,data');
fclose(f);
And you can also simplify your collection of data from textscan by doing either A = [data{:}] or by providing the CollectOutput flag:
data = textscan(fid,'%f %f %f %f %f %f %f','HeaderLines',1,'CollectOutput',true);
A = data{1};
But one question: are you doing anything with the data in A or just writing it back out again? If the latter, here's a function to do it for you
function replaceHeader(filein,fileout,header)
fid = fopen(filein);
x = textscan(fid,'%s');
fclose(fid);
n = length(header);
fmt = [repmat('%-10s\t',1,n-1),'%-10s\n'];
y = [header,x{1}{(n+1):end}];
fid = fopen(fileout,'w');
fprintf(fid,fmt,y{:});
fclose(fid);
Then
replaceHeader('u001_s01_sign_ds2-tb-0c_01.svc','u001_s01_sign_ds2-tb-0c_01.svc', {'X' 'Y' 'Z' 'A' 'B' 'C' 'D'})
(If you were always going to overwrite the file, you could obviously simplify the function to use one filename.)
EDIT TO ADD: Based on the comments, it looks like this should do the job:
function replaceHeader3(filein,fileout,header) 
fid = fopen(filein,'r'); 
data = textscan(fid,'%s','HeaderLines',1); 
fclose(fid); 
n = length(header); 
fmt = [repmat('%-10s\t',1,n-1),'%-10s\n']; 
y = [header,data{1}{:}]; 
fid = fopen(fileout,'w'); 
fprintf(fid,fmt,y{:}); 
fclose(fid);
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