Invalid file identifier. Use fopen to generate a valid file identifier.

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Mainul Hoque 2020-9-8

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https://ww2.mathworks.cn/matlabcentral/answers/590437-invalid-file-identifier-use-fopen-to-generate-a-valid-file-identifier

编辑： Stephen23 2020-9-8

test.txt

Hi

I am using the following code to read a file and delete the three headres and footers lines from the dat. file. But unfortunately it shows the following error. Can anybody helpme to this issue please.

Error: " Error using textscan

Invalid file identifier. Use fopen to generate a valid file identifier."

clear;clc;close all
vec_dir='Z:\Flotation_chamber\8.0Volts\';
vectors=dir([vec_dir '*.dat']);
num_files=size(vectors,1);
for img_no=1:num_files
    disp(['img :' num2str(img_no)]);
    vector_nm=vectors(img_no).name;
    
    % phase 1 : read the ith dat file
    fid = fopen(vector_nm,'r');
    TextDat = textscan(fid,'%s','delimiter','\n');
    fclose(fid);
    
    % phase 2 : just take from the 4th line (3 headers) until the end-3
    % (3 footers)
    NewTextDat = TextDat{1}(3+1:end-3);
    
    % phase 3 : rewrite the file with the new data
    fid = fopen(vector_nm,'wt');
    fprintf(fid,'%s\n',NewTextDat{:});
    fclose(fid);
end

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Mainul Hoque 2020-9-8

I have tried to attached .dat file but unfortunately I cann't. So I change the type of data file to .txt. Thanks

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Answer 1

Stephen23 2020-9-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/590437-invalid-file-identifier-use-fopen-to-generate-a-valid-file-identifier#answer_491323

编辑：Stephen23 2020-9-8

在 MATLAB Online 中打开

You need to use the directory information in two locations: both with dir and with fopen, e.g.:

vec_dir = 'Z:\Flotation_chamber\8.0Volts\';
vectors = dir(fullfile(vec_dir,'*.dat'));
...
    vector_nm = fullfile(vec_dir,vectors(img_no).name);

As the fopen documentation states "If the file is not in the current folder, filename must include a full or a relative path." You did not provide the path to fopen, so it only looks in the current directory.