Error while using function readtable()

Question

Zhenyu Huang 2023-10-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2031939-error-while-using-function-readtable

编辑： Zhenyu Huang 2023-10-12

dyw_e_u.zip

I use function readtable to read a txt file, it works well before, but suddenly it don't works anymore and return the error:

>> a2=readtable('dyw_e_u.txt');
Error using readtable
inputs must be a string array, character vector, or cell array of character vectors. 
>> a2=readtable("dyw_e_u.txt");
Error using readtable
inputs must be a string array, character vector, or cell array of character vectors.

I think what I input 'dyw_e_u.txt' is a character vector, I don't understand why it return the error, please help, thanks

My text file is like this:

Lat Lon mm.dd.yyyy hh:mm:ss U(m^2/s) V(m^2/s) u(cm/s) v(cm/s) Depth(m)

22.4189 114.9908 2021/5/31 0:00:00 -1.123 1.949 -4.16 7.22 26.993

22.4189 114.9908 2021/5/31 1:00:00 -0.452 1.484 -1.675 5.497 26.993

22.4189 114.9908 2021/5/31 2:00:00 0.361 1.06 1.338 3.926 26.993

22.4189 114.9908 2021/5/31 3:00:00 0.994 0.838 3.684 3.104 26.993

22.4189 114.9908 2021/5/31 4:00:00 1.353 0.544 5.014 2.017 26.993

22.4189 114.9908 2021/5/31 5:00:00 1.597 -0.203 5.917 -0.754 26.993

22.4189 114.9908 2021/5/31 6:00:00 1.916 -1.429 7.097 -5.293 26.993

22.4189 114.9908 2021/5/31 7:00:00 2.289 -2.645 8.482 -9.798 26.993

22.4189 114.9908 2021/5/31 8:00:00 2.466 -3.196 9.137 -11.84 26.993

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Dyuman Joshi 2023-10-11

在 MATLAB Online 中打开

dyw_e_u.zip

It's working here.

unzip('dyw_e_u.zip')
mat = readtable('dyw_e_u.txt')
Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.
Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.
mat = 42295×11 table
     Lat       Lon       mm_dd_yyyy      hh_mm_ss    U_m_2_s_    V_m_2_s_    u_cm_s_    v_cm_s_    Depth_m_      Var10         Var11   
    ______    ______    _____________    ________    ________    ________    _______    _______    ________    __________    __________

    22.419    114.99    {'2021/5/31'}    00:00:00     -1.123       1.949      -4.16        7.22     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    01:00:00     -0.452       1.484     -1.675       5.497     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    02:00:00      0.361        1.06      1.338       3.926     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    03:00:00      0.994       0.838      3.684       3.104     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    04:00:00      1.353       0.544      5.014       2.017     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    05:00:00      1.597      -0.203      5.917      -0.754     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    06:00:00      1.916      -1.429      7.097      -5.293     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    07:00:00      2.289      -2.645      8.482      -9.798     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    08:00:00      2.466      -3.196      9.137      -11.84     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    09:00:00      2.188      -2.792      8.104     -10.344     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    10:00:00      1.446      -1.748      5.355      -6.475     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    11:00:00      0.529      -0.712      1.958      -2.639     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    12:00:00     -0.198      -0.135     -0.734        -0.5     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    13:00:00     -0.576       0.045     -2.133       0.166     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    14:00:00     -0.745       0.222     -2.759       0.824     26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    15:00:00     -0.964       0.658     -3.573       2.436     26.993     {0×0 char}    {0×0 char}

What is the output when you run this snippet of code in your MATLAB?

which readtable -all
/MATLAB/toolbox/matlab/iofun/readtable.m
/MATLAB/toolbox/shared/io/general/+matlab/+io/@ImportOptions/ImportOptions.m  % matlab.io.text.DelimitedTextImportOptions method

dpb 2023-10-11

在 MATLAB Online 中打开

dyw_e_u.zip

unzip dyw_e_u.zip
delete dyw_e_u.zip
a2=readtable('dyw_e_u.txt');
Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.
Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.
head(a2)
     Lat       Lon       mm_dd_yyyy      hh_mm_ss    U_m_2_s_    V_m_2_s_    u_cm_s_    v_cm_s_    Depth_m_      Var10         Var11   
    ______    ______    _____________    ________    ________    ________    _______    _______    ________    __________    __________

    22.419    114.99    {'2021/5/31'}    00:00:00     -1.123       1.949      -4.16       7.22      26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    01:00:00     -0.452       1.484     -1.675      5.497      26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    02:00:00      0.361        1.06      1.338      3.926      26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    03:00:00      0.994       0.838      3.684      3.104      26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    04:00:00      1.353       0.544      5.014      2.017      26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    05:00:00      1.597      -0.203      5.917     -0.754      26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    06:00:00      1.916      -1.429      7.097     -5.293      26.993     {0×0 char}    {0×0 char}
    22.419    114.99    {'2021/5/31'}    07:00:00      2.289      -2.645      8.482     -9.798      26.993     {0×0 char}    {0×0 char}

As the others have shown, it's not a syntax issue; more than likely as @Dyuman Joshi was poking at you've aliased the readtable function accidentally.

Besides his suggestion to see what which returns, simply enter

clear readtable

at the command line and try again. That should fix it; if it doesn't, you may have somehow manged to corrupt the install, but that would be highly unlikely--not impossible, but not probable.

Zhenyu Huang 2023-10-12

编辑：Zhenyu Huang 2023-10-12

在 MATLAB Online 中打开

ladcp.zip

I fix it.

I try which and clear in the command line：

>> which readtable -all
D:\Program File\MATLAB\R2022b\toolbox\matlab\iofun\readtable.m
D:\Program File\MATLAB\R2022b\toolbox\shared\io\general\+matlab\+io\@ImportOptions\ImportOptions.m  % matlab.io.ImportOptions method
>> clear readtable
>> which readtable -all
D:\Program File\MATLAB\R2022b\toolbox\matlab\iofun\readtable.m
D:\Program File\MATLAB\R2022b\toolbox\shared\io\general\+matlab\+io\@ImportOptions\ImportOptions.m  % matlab.io.ImportOptions method
>> a2=readtable('dyw_e_u.txt');
Error using readtable
inputs must be a string array, character vector, or cell array of character vectors. 

It still can't work.

I remember that the problem occur after I add a big folder and its subfolder to matlab's search path, so I remove it from search path and try again, now the readtable works! I try many times and finally locate the problem in a folder, if this folder in the search path, the readtable function can't work. But there are no functions or scripts name "readtable" in this folder. I put it here if anybody have interest to figure out why. Thanks everyone reply my question.

Image Analyst 2023-10-12

在 MATLAB Online 中打开

"if it is in the path the readtable function can't work. But there are no functions or scrips name readtable in this folder. I put it here if anybody have interest to figure out why. " <== that is not true. I took a file and moved it out of the current folder and into a different folder that is still in the search path. It found it and read it in.

Nonetheless we recommend that you not depend on the data folder being in the search path and for you to construct the full path (folder + base file name + extension) using the fullfile function. That way it will definitely find it.

help fullfile
 FULLFILE Build full file name from parts.
    F = fullfile(FOLDERNAME1, FOLDERNAME2, ..., FILENAME) builds a full
    file specification F from the folders and file name specified. Input
    arguments FOLDERNAME1, FOLDERNAME2, etc. and FILENAME can be strings,
    character vectors, or cell arrays of character vectors. Non-scalar
    strings and cell arrays of character vectors must all be the same size.
 
    If any input is a string array, F is a string array. Otherwise, if any
    input is a cell array, F is a cell array.  Otherwise, F is a character
    array.
 
    The output of FULLFILE is conceptually equivalent to character vector
    horzcat operation:
 
       F = [FOLDERNAME1 filesep FOLDERNAME2 filesep ... filesep FILENAME]
 
    except that care is taken to handle the cases when the folders begin or
    end with a file separator.
 
    FULLFILE collapses inner repeated file separators unless they appear at 
    the beginning of the full file specification. FULLFILE also collapses 
    relative folders indicated by the dot symbol, unless they appear at 
    the end of the full file specification. Relative folders indicated 
    by the double-dot symbol are not collapsed.
 
    To split a full file name into folder parts, use split(f, filesep).
 
    Examples
      % To build platform dependent paths to files:
         fullfile(matlabroot,'toolbox','matlab','general','Contents.m')
 
      % To build platform dependent paths to a folder:
         fullfile(matlabroot,'toolbox','matlab',filesep)
 
      % To build a collection of platform dependent paths to files:
         fullfile(toolboxdir('matlab'),'iofun',{'filesep.m';'fullfile.m'})
 
    See also FILESEP, PATHSEP, FILEPARTS, GENPATH, PATH, SPLIT.

    Documentation for fullfile
       doc fullfile

Walter Roberson 2023-10-12

在 MATLAB Online 中打开

I suggest you use

dbstop if error

and run your code, and then when it stops at the error line, start working backwards to trace the cause.

Ayush Gupta 2023-10-12

I am also not facing any issue in R2022b as well as R2023a.

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Error while using function readtable()

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Error while using function readtable()

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