Accessing table variables in a class method

Question

Corinne Gard 2019-8-27

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/477691-accessing-table-variables-in-a-class-method

评论： Matt J 2019-8-29

I have some tabular data with variable names for the columns in my main file. I am passing the tables as variables into methods in a class. In those methods, I wish to be able to access and edit the tabular data according to the variables. How can I do this?

Here is the section of code in my main file (T_n, T_l and period are previously set)

% Get data   
lab_Data = readtable(file_lab, 'FileType', 'text');
lab_Data.Properties.VariableNames = {'Time', 'Flow', 'P_diff', 'Vol_ex'};
nalm_Data = readtable(file_nalm,'Sheet', sheet_name{4});
nalm_Data.Properties.VariableNames = {'Time', 'P_diff', 'Flow', 'Vol_tid'};
%Run tests
test1 = Tester(nalm_Data, lab_Data, T_n, T_l, period);
fileTrimmer(test1);
setFile(test1);

The construction of test1 is successful using a simple constructor. However, the other methods don't run and the error message appears to be directed at my attempt to access variables according to their names.

Here is a sample of my "fileTrimmer" code

 function fileTrimmer(obj)
            ...
            %trim nalm to first peak
            f_nalm = obj.nalm_Data.Flow; 
            t_nalm = obj.nalm_Data.Time;
            [~, loks] = findpeaks(f_nalm, t_nalm, 'MinPeakDistance', obj.period/2);
            p1 = loks(1); % seconds of first peak.

Here is the constructor

      classdef Tester
    
        properties
            sam_rate = .05
            %Errors for FlowLab
            erFLflow = .05 %(sl/min)
            erFLvol = .01 %sl
            erFLdp = .1 %mbar
            erFLfreq = 1 %bpm
            erFLcomp = 1 %ml/mbar
            
            newFile
            
            nalm_Data
            lab_Data
            T_n
            T_l
            period            
            
         end
    
    methods
        function obj = Tester(nalm_Data, lab_Data, T_n, T_l, period) 
        
        obj.nalm_Data = nalm_Data;
        obj.lab_Data = lab_Data;
        obj.T_n = T_n;
        obj.T_l = T_l;
        obj.period = period;
        
               
        fprintf("Tester worked\n");
     
        end

Edit: I actually managed to get around this issue by accessing table data by column indice rather than by their names, so as such have bypassed the error. I definately am still interested to know why it didn't work initially as well as whether it's best to use a value or handle class.

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Corinne Gard 2019-8-29

No. Do you think it would be best if I had one? To be honest I am new to oop in Matlab, I am much more familiar with Java.

Matt J 2019-8-29

No, but if you had defined a subsref method, it could explain any unexpected indexing behavior.

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Answer 1

Catalytic 2019-8-29

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/477691-accessing-table-variables-in-a-class-method#answer_389614

编辑：Catalytic 2019-8-29

在 MATLAB Online 中打开

Here is an example to demonstrate that accessing tables by variable name works fine with value classes. Subclassing from 'handle' will also give the same result.

classdef myclass
  
    properties 
       T  %table prooperty
    end
    methods 
        
        function obj=myclass(T)
          obj.T=T;
        end
        
        function accessT(obj)
            obj.T.Var2,
        end
    
    end
    
end

T =
  5×3 table
    Var1    Var2    Var3
    ____    ____    ____
     1        6      11 
     2        7      12 
     3        8      13 
     4        9      14 
     5       10      15 
     
     
>> obj=myclass(T)
>> obj.accessT
ans =
     6
     7
     8
     9
    10