How to assign the number of filled columns of a text file as the value of a variable

Question

Hugo 2020-9-21

0
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https://ww2.mathworks.cn/matlabcentral/answers/597166-how-to-assign-the-number-of-filled-columns-of-a-text-file-as-the-value-of-a-variable

回答： Walter Roberson 2020-9-21

Hello,

I am trying to open the file nt.txt, with the goal of assigning the number of columns to the variable nu. Right now, I have the following code:

fid=fopen('E:\A\nt.txt');
g = textscan(fid,'%d','delimiter','\n');
nu=length(g)
fclose(fid)

However, it does not seem to work. Could someone help me?

Best regards,

Hugo

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Answer 1

Walter Roberson 2020-9-21

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https://ww2.mathworks.cn/matlabcentral/answers/597166-how-to-assign-the-number-of-filled-columns-of-a-text-file-as-the-value-of-a-variable#answer_497839

在 MATLAB Online 中打开

detectImportOptions() might be your easiest method.

Otherwise,

fid = fopen('E:\A\nt.txt');
while true
  thisline = fgetl(fid);
  if ~ischar(thisline); break; end      %end of file
  thisline = strtrim(thisline);
  if ~isempty(thisline); break; end     %found a line
end
fclose(fid);
if ~ischar(thisline)
    nu = 0;
else
    nu = length(regexp(thisline, '\S+', 'split'));
end

This code assumes that columns are delimited by whitespace (otherwise your %d format would have failed).

The code looks for the first line of the file that contains something that is not whitespace, splits it into fields, and assumes that the number of columns is however many fields were found.

If the file has no non-empty lines, then nu is assigned 0.