How to detect, open and process nxm matrices?

Question

Ekin 2013-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/87278-how-to-detect-open-and-process-nxm-matrices

Hi i have a code to open .txt files with nx1 matrices, it works very well:

[filename1,filepath1]=uigetfile({'*.txt*','Text Files'},...
  'Select Data File 1');
   cd(filepath1);
 fp= fopen(filename1);
 fgets(fp); 
 A = textscan(fp, '%f');
 fclose(fp);
 result=A{:};

But i want to open 1xm matrices with this code also. Do do this, i though to create an if-else structure to deteckt if the data matrix is nx1 or 1xm and then textscan it with textscan(fp, '%f') or textscan(fp, '%??'). Or is there another way to make this without creating an if-else structure? Thanks in advance!

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Answer 1

Jan 2013-9-17

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https://ww2.mathworks.cn/matlabcentral/answers/87278-how-to-detect-open-and-process-nxm-matrices#answer_97018

编辑：Jan 2013-9-17

在 MATLAB Online 中打开

fp = fopen(filename1);
if fp == -1, error('Cannot open %s', filename1); end
fgets(fp);  % Skipping a header line?!
pos = ftell(fp);
tmpLine = fgets(fp);  % Read first line
tmpData = sscanf(tmpLine, '%g ', Inf);
nDataPerLine = length(tmpData);
fseek(fp, pos, -1);  % Spool one line back
Data = fscanf(fp, '%g ', [nDataPerLine, Inf]);
fclose(fp);

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Answer 2

Azzi Abdelmalek 2013-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/87278-how-to-detect-open-and-process-nxm-matrices#answer_96815

在 MATLAB Online 中打开

If your files are not big, you can use

v=dlmread('file.txt')

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Ekin 2013-9-15

And files will be really big.

Jan 2013-9-17

编辑：Jan 2013-9-17

uigetfile does not open files, but determine the file name only. Of course you can apply Azzi's suggestion together with your uigetfile part.

Some users think, that 1MB is big, others use this term for 20 TB files.

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Answer 3

Walter Roberson 2013-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/87278-how-to-detect-open-and-process-nxm-matrices#answer_96816

在 MATLAB Online 中打开

textscan(fp, '%f')

is fine to read either format. End-of-line is considered to be "whitespace" for textscan(), so it will be fine without you having to code differently for the two situations.

If it is important that you process the two forms in different ways, then:

currentloc = ftell(fp);  %find out where we are now
small_input = fread(fp, 20, '*uint8');   %read a little
fseek(fp, currentloc, 'bof');  %go back to where we were
if any(small_input == 10)    %control J, newline, \n
  %there was a newline, so it is n x 1 rather than 1 x n.
  ...
else
  %it was 1 x n
end