Read a Special Text File

Question

AEW 2022-4-22

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1702760-read-a-special-text-file

评论： AEW 2022-4-23

I was wondering if there is a quick way to read the following text file sample where the first data line starts with a bracket. I would like to avoid the hassle of manually removing the bracket from every file I obtain. I use the following command for now after I remove the bracket.

Thanks.

data = textscan(Fopen, '%d %f %d %d %d;', 'HeaderLines',2)

file.txt

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Stephen23 2022-4-23

A simple and very efficient approach would be to simply define the square bracket as whitespace, which you can do using TEXTSCAN's WHITESPACE option. Another good approach would be to use a fixed-width import via READTABLE.

Using STR2NUM is not very efficient.

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Answer 1

Stephen23 2022-4-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1702760-read-a-special-text-file#answer_949320

编辑：Stephen23 2022-4-23

在 MATLAB Online 中打开

textfile.txt

Here are two much more efficient approaches.

The first is exactly like you are doing now, just adding the WHITESPACE option to efficiently ignore the square bracket:

fnm = 'textfile.txt';
fmt = '%d%f%d%d%d;';
opt = {'HeaderLines',2, 'Whitespace',' \t['};
fid = fopen(fnm,'rt');
data = textscan(fid, fmt, opt{:})
data = 1×5 cell array
    {11130×1 int32}    {11130×1 double}    {11130×1 int32}    {11130×1 int32}    {11130×1 int32}
fclose(fid);

The second is to import the file as table, which has headers and may be more convenient to access:

opt = detectImportOptions(fnm, 'FileType','fixedwidth', ...
    'VariableWidths',[6,9,16,16,16], 'VariableNamesLine',1, ...
    'VariableNamingRule','preserve', 'Range',3, 'Whitespace',' [', ...
    'ExtraColumnsRule','ignore');
tbl = readtable(fnm,opt)
tbl = 11130×5 table
SampleTimeCommanded PosEncoder 1 PosEncoder 2 Pos__________________________________________________

       0          0          0                0                0      
       1      0.001          0                0                0      
       2      0.002          0                0                0      
       3      0.003          0                1                0      
       4      0.004          0                4                0      
       5      0.004          0                7                0      
       6      0.005          0               14                0      
       7      0.006          0               20                0      
       8      0.007          0               27                0      
       9      0.008          0               37                0      
      10      0.009          0               47                0      
      11       0.01          0               57                1      
      12      0.011          0               66                3      
      13      0.012          0               76                4      
      14      0.012          0               87                6      
      15      0.013          0               98                7      

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AEW 2022-4-23

Thank you!

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Answer 2

Voss 2022-4-22

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1702760-read-a-special-text-file#answer_948655

编辑：Voss 2022-4-22

在 MATLAB Online 中打开

textfile.txt

% read file into character vector data
data = fileread('textfile.txt');
% remove the first two lines
idx = find(data == newline(),2);
data(1:idx(end)) = [];
% convert to numeric
M = str2num(data);
% show some results
format long
disp(M(1:10,:));
                   0                   0                   0                   0                   0
   1.000000000000000   0.001000000000000                   0                   0                   0
   2.000000000000000   0.002000000000000                   0                   0                   0
   3.000000000000000   0.003000000000000                   0   1.000000000000000                   0
   4.000000000000000   0.004000000000000                   0   4.000000000000000                   0
   5.000000000000000   0.004000000000000                   0   7.000000000000000                   0
   6.000000000000000   0.005000000000000                   0  14.000000000000000                   0
   7.000000000000000   0.006000000000000                   0  20.000000000000000                   0
   8.000000000000000   0.007000000000000                   0  27.000000000000000                   0
   9.000000000000000   0.008000000000000                   0  37.000000000000000                   0
disp(M(end-9:end,:));
   1.0e+05 *

   0.111200000000000   0.000098460000000                   0   1.003280000000000   0.222970000000000
   0.111210000000000   0.000098470000000                   0   1.002280000000000   0.222750000000000
   0.111220000000000   0.000098480000000                   0   1.001270000000000   0.222530000000000
   0.111230000000000   0.000098480000000                   0   1.000280000000000   0.222310000000000
   0.111240000000000   0.000098490000000                   0   0.999280000000000   0.222090000000000
   0.111250000000000   0.000098500000000                   0   0.998290000000000   0.221870000000000
   0.111260000000000   0.000098510000000                   0   0.997310000000000   0.221640000000000
   0.111270000000000   0.000098520000000                   0   0.996330000000000   0.221420000000000
   0.111280000000000   0.000098530000000                   0   0.995360000000000   0.221190000000000
   0.111290000000000   0.000098540000000                   0   0.994390000000000   0.220970000000000