Dot indexing is not supported for variables of this type.

Question

Pras 2021-5-26

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评论： Walter Roberson 2024-4-7，17:09

DT_steadystate.m

Dear all,

I am very new to Matlab. How can I fix the error of "Dot indexing is not supported for variables of this type" in the following code? Thank you.

global M_ 
% read out parameters to access them with their name
NumberOfParameters = M_.param_nbr;
for ii = 1:NumberOfParameters
  paramname = deblank(M_.param_names(ii,:));
  eval([ paramname ' = M_.params(' int2str(ii) ');']);
end
% initialize indicator
check = 0;

The error:

Dot indexing is not supported for variables of this type.

Error in DT_steadystate (line 7)

NumberOfParameters = M_.param_nbr;

Best,

Pras

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Marwan Soliman 2022-5-4

filename='pulse.txt';
delimiterIn='';
headerlinesIN= 1;
A=importdata(filename,delimiterIn,headerlinesIN);
Led_R = A.data(:,1); % RED (R)
Led_IR = A.data(:,2); % INFRARED (IR)

Dot indexing is not supported for variables of this type.

anyone can help plz line 5

Walter Roberson 2022-5-4

@Marwan Soliman

I recommend against using importdata(), as the fundamental datatype that is output is too unpredicatable.

When you use importdata() with a file that is pure numeric after the given header lines, then the output is a pure numeric array.

But if you use importdata() with a file that has additional headers after the given header lines, then the output is a struct.

And if you use importdata() with a file that has a mix of text and numbers, then the output is a struct and the struct has additonal fields compared to the case of a header followed by pure numberic.

I recommand that you use readmatrix() instead for your situation.

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Answer 1

Pras 2021-5-26

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Thank you all for the reply. I am learning Matlab from this replication file of a journal article.

From another forum, I found that by including the following, it will work:

if isfield(M_,'param_nbr') == 1
    
end

Thanks!

Best,

Pras

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Answer 2

Allen 2021-5-26

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It appears that you are initializing a new variable M_ at the start of your code and by default it is just an empty double-class array. Doubles do not use or allow dot notation. Also, is there a reason why you are trying to initialize your variable as a global variable? If not, then I would recommend steering away from a global as this can create problems in subsquently run scripts if you are not careful.

clear
global M_
whos('M_')
  Name      Size            Bytes  Class     Attributes

  M_        0x0                 0  double    global    

If you are intending for M_ to utilize the dot notation in MATLAB, then you will need to generate a table or structure class. See help documents for struct and table classes.

help struct
help table

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Pras 2021-5-26

Thank you all for the reply. I am learning Matlab from this replication file of a journal article.

From another forum, I found that by including the following, it will work:

if isfield(M_,'param_nbr') == 1
    
end

Thanks!

Best,

Pras

Allen 2021-5-26

Pras,

You should what you found as a solution to you question and accept your own response as the correct solution. This will help other people that are looking for a similar answer know what works.

Thanks,

Allen

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Answer 3

Tapamay 2024-4-6，12:21

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Hello Everyone,

I am new to Matlab. How can I fix the error of "Dot indexing is not supported for variables of this type" in the following code? Thank you.

The error shows this:

Dot indexing is not supported for variables of this type.

Error in RawData_To_CpVsAoA (line 13)

rawdata=rawdata.data(1:10,1:24);

clc; clear all; close all;
aoa=[-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30];
Cp_aoa_data=[];
for i=1:length(aoa)
    filename = ['Raw Data\',num2str(aoa(i)),'.txt'];
    rawdata=importdata(filename);
    rawdata=rawdata.data(1:10,1:24);
    rawdata=mean(rawdata,1);
    airfoilpressure=rawdata(1:22)*792*9.81/1000;
    p_inf=rawdata(24)*792*9.81/1000;
    p_0=-2.338*792*9.81/1000;
    Cp = (airfoilpressure - p_inf)/(p_0-p_inf);
    Cp_aoa_data=[Cp_aoa_data Cp'];
end
Error using importdata (line 139)
Unable to open file.

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Walter Roberson 2024-4-7，17:09

The data type returned by importdata() depends on the format of the file. If it happened to be something that looked like a numeric block, then importdata() would return a numeric array, and numeric arrays do not allow dot indexing.

We recommend that you use readtable() or readmatrix() or readcell() instead of importdata()

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