Importing table from text file and matching header to column

Question

Lucas Wong 2022-3-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1675724-importing-table-from-text-file-and-matching-header-to-column

评论： Lucas Wong 2022-3-21

采纳的回答： AndresVar

example_data.txt

在 MATLAB Online 中打开

Hi everyone,

Here is an example of my data:

#    r              CAC-CAC                       CAC-OAC                  
2700000E+01  0.0000000E+00  0.0000000E+00  0.3860216E-03  0.2814651E-01
2730000E+01  0.0000000E+00  0.0000000E+00  0.3775852E-03  0.2753156E-01
2760000E+01  0.0000000E+00  0.0000000E+00  0.5541359E-02  0.1041859E+00
2790000E+01  0.0000000E+00  0.0000000E+00  0.7230470E-02  0.1176749E+00
2820000E+01  0.0000000E+00  0.0000000E+00  0.1096994E-01  0.1432550E+00
2850000E+01  0.0000000E+00  0.0000000E+00  0.1870899E-01  0.1847078E+00

I would like to import my data into a table, with the text in the first row used as a variable for each column that it lines up with. The unwanted "#" character and the inconsistent spacing at the start of the first row means that readtable(example_data.txt); does not does not produce the correct headers for the table and instead leads to Var1, Var2,..., ect.

For example, in Excel the import data option slices up the data and the headers end up in the correct location in the imported table:

Note that some of the columns do not have headers and I do not require this data in my imported table.

I am very new to MATLAB, so any help is very appreciated!

Cheers!

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Answer 1

AndresVar 2022-3-20

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1675724-importing-table-from-text-file-and-matching-header-to-column#answer_922129

编辑：AndresVar 2022-3-20

在 MATLAB Online 中打开

example_data.txt

I tried the import tool: Import data from file - MATLAB (mathworks.com)

The code it generated for your data did not look as pretty as it usually does, but seems to do the job.

Edit: noticed the import tool detected 'fixedwidth' filetype, but readtable seems to detect 'delimitedtext'. So you can specify fixedwidth in the options. The variablenamingrule option doesn't seem necessary but there is a warning without it.

opts = detectImportOptions('example_data.txt',FileType='fixedwidth',VariableNamingRule='preserve');
t1 = readtable("example_data.txt",opts)
t1 = 6×6 table
        #          r      CAC-CAC    Var4     CAC-OAC        Var6  
    __________    ____    _______    ____    __________    ________

    {0×0 char}     2.7       0        0      0.00038602    0.028147
    {0×0 char}    2.73       0        0      0.00037759    0.027532
    {0×0 char}    2.76       0        0       0.0055414     0.10419
    {0×0 char}    2.79       0        0       0.0072305     0.11767
    {0×0 char}    2.82       0        0         0.01097     0.14325
    {0×0 char}    2.85       0        0        0.018709     0.18471
t1.("#")=[] % remove the # column
t1 = 6×5 table
     r      CAC-CAC    Var4     CAC-OAC        Var6  
    ____    _______    ____    __________    ________

     2.7       0        0      0.00038602    0.028147
    2.73       0        0      0.00037759    0.027532
    2.76       0        0       0.0055414     0.10419
    2.79       0        0       0.0072305     0.11767
    2.82       0        0         0.01097     0.14325
    2.85       0        0        0.018709     0.18471

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AndresVar 2022-3-20

编辑：AndresVar 2022-3-20

在 MATLAB Online 中打开

@Lucas Wong there is an extra space at the end of the first row that messes it up. BUT looks like just specificying VariableNamesLine=1 sorta solves the problem.

opts = detectImportOptions('example_data2.txt', ...
    FileType='fixedwidth',VariableNamingRule='preserve', ...
    VariableNamesLine=1 );
% optional: sanitize the variable names by removing white spaces and
% replacing unwanted characters.
opts.VariableNames = strtrim(strrep(strrep(opts.VariableNames,...
    '-','_'), '#','')); 
t1 = readtable("example_data2.txt",opts)
figure;
plot(t1.r,t1.CAC_CAC);