how to solve the fopen error?

24 次查看（过去 30 天）
Lilya
Lilya 2017-8-17
评论： Lilya 2017-8-17
Hi all,
I've done the below code to read .txt files and extracting columns from each one. the error appears just from the second to the rest of files. Could anyone help me with this?
thank you
Error using fgets
Invalid file identifier. Use fopen to generate a valid file identifier.
Error in RUV_readFile (line 21)
line = fgets(file1);
clc
clear all
close all
%read file line by line
%loop over the files from list
%open each file and loop over the lines,
files_str = fileread('foldername/files.txt');
list = splitlines(files_str);
for k=1:length(list)
filename = list{k}; %index cell array of filenames using k
disp(filename);
file1 = fopen(strcat('foldername',filename));
filemat = [];
line = fgets(file1);
while ischar(line)
if isempty(strfind(line,'%')) %if line doesn't contains %
vec = str2num(line); %convert line string to vector
filemat = [filemat;vec]; %fill matric from vectors in file
end
% disp(line)
line = fgets(file1);
end
fclose(file1);
cols = filemat(:,1:4);
save(strcat('output/',filename), 'cols', '-ascii')
end
  3 个评论
显示 1更早的评论
Stephen23
Stephen23 2017-8-17
编辑：Stephen23 2017-8-17
@Guillaume: thank you for the detailed explanation. It was remiss of me to not explain as much as you did.
@Lina Eyouni: you should read the MATLAB documentation, which shows just how simple this should be:
https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html
https://www.mathworks.com/help/matlab/import_export/ways-to-import-text-files.html
Lilya
Lilya 2017-8-17
Thanks Guillaume I am applying this now but without the apostrophes, it gives me an error. but I am working now with reading it from the links above. the other thing that I would like to clarify is the folder name. the name above is just to show the case because mine here is too long. I apologize.
thank you once again

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Stephen23
Stephen23 2017-8-17
编辑：Stephen23 2017-8-17
  1. Use fullfile instead of the rather inappropriate strcat.
  2. Return the second output of fopen and check this using assert.
[file1,msg] = fopen(fullfile('foldername',filename));
assert(file1>=3,msg)
  8 个评论
显示 6更早的评论
Stephen23
Stephen23 2017-8-17
编辑：Stephen23 2017-8-17
Then you have no problem. If the first output is >=3 then fopen successfully opened the file.
Note that you should replace ischar:
while ischar(line)
with feof:
while ~feof(file1)
Also note that this:
line = fgets(file1);
while ischar(line)
if isempty(strfind(line,'%')) %if line doesn't contains %
vec = str2num(line); %convert line string to vector
filemat = [filemat;vec]; %fill matric from vectors in file
end
% disp(line)
line = fgets(file1);
end
is a very inefficient way to read numeric data into MATLAB. You have not described what format the files have, but you should really consider using the inbuilt functions for reading numeric data:
https://www.mathworks.com/help/matlab/standard-file-formats.html
Lilya
Lilya 2017-8-17
Ok. I will try with this now. Thank you so much for your response and help

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Characters and Strings 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by