how to extract data from an text file?

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isamh
isamh 2020년 2월 3일
댓글: Walter Roberson 2020년 2월 14일
I have two files, one in excel and one in a text file, how would i obtain column data from the text file even though i did it from an excel file.
code is:
filename = 'mct.xlsx'
data = xlsread(filename, 'mct', 'A:D');
Phase1 = data(data(:4)==1,:);
how would i be able to extract this from a text file?

채택된 답변

fred  ssemwogerere
fred ssemwogerere 2020년 2월 3일
Hello, there are a number of ways to go about this. Please refer to the following links:
  댓글 수: 1
isamh
isamh 2020년 2월 3일
편집: isamh 2020년 2월 3일
saw this example and had several questions
x = 100*rand(8,1);
fileID = fopen('nums1.txt','w');
fprintf(fileID,'%4.4f\n',x);
fclose(fileID);
what does the 'w' mean?
also, what does ''%4.4f\n'' mean?

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추가 답변(3개)

fred  ssemwogerere
fred ssemwogerere 2020년 2월 4일
% what does the 'w' mean?
'w' gives write access permission to the file
% also, what does ''%4.4f\n'' mean?
This is a formatting operator that prints each input as a fixed point number having field width of 4, and the number of digits after the decimal point of 4, before proceeding to a new line ("\n").
  댓글 수: 8
Walter Roberson
Walter Roberson 2020년 2월 5일
Sometimes you can use textscan CommentStyle to ignore headers if they always have the same start and stop. Otherwise sometimes you end up looping textscan, especially if you want the blocks to be separated in output.
Another method that can be very useful is to fileread() the entire file as a character vector, and then use a combination of regexp and regexprep to extract parts of it, possibly then passing the resulting characters into textscan.

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isamh
isamh 2020년 2월 5일
will try that out, thanks for everything Walter!

isamh
isamh 2020년 2월 12일
편집: isamh 2020년 2월 12일
Hey Walter, I tried to ignore any text that appears within the TXT file but kept getting an error message.
Code:
result = [];
fid=fopen('MCT_Data.txt');
tic
while 1
tline = fgetl(fid);
if ~ischar(tline), break, end
celldata = textscan(tline,'%f %f %f %f %f %f');
matdata = cell2mat(celldata);
% match fails for text lines, textscan returns empty cells
result = [result ; matdata];
end
toc
fclose(fid);
the error message is:
Error using textscan.
First input can not be empty. Expected a non-empty character vector or a valid file-id.
so, the two rows contain
R E V D
m k h -
435 345 435 3543
...
the file has alot of numerical data. the headers repeat randomly and are the same every time they repeat.
how would ignore everything but numerical data?
  댓글 수: 3
Walter Roberson
Walter Roberson 2020년 2월 14일
result = [];
fid=fopen('MCT_Data.txt');
tic
while 1
tline = fgetl(fid);
if ~ischar(tline); break; end %end of file
if isempty(tline); continue; end %empty line
celldata = textscan(tline,'%f %f %f %f %f %f');
matdata = cell2mat(celldata);
% match fails for text lines, textscan returns empty cells
result = [result ; matdata];
end
toc
fclose(fid);
What is your file format? It appears that you have text at the beginning of some of the lines, and you are doing this looping so that you can ignore those lines? There are usually easier ways to deal with such files.

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