How can I assign a single column of a 0x10 empty table

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Rafael Cordero 2021-11-29

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回答： Star Strider 2021-11-29

Hello folks,

I have a 0x10 empty table. That is: the table variables are declared but there is no actual data entries in the table. Let's call it

myTable

I am trying to assign the first column of the table like so:

myTable.firstVariable = [0:1:length(x)]';

But alas this returns the following error:

To assign to or create a variable in a table, the number of rows must match the height of the table.

Of course, the height of the table is currently 0. Its height will be dictated by another variable x. I do not care what the other variables will be populated with at this time (i.e. [], or 0, or NaN, or whatever), I will populate them later.

How can I assign the first variable?

Thank you!

PS: I cannot use a struct or array. The datatype must remain as a table.

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Answer 1

Star Strider 2021-11-29

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在 MATLAB Online 中打开

Preallocation for table arrays is possible.

myTable = table('Size',[10 1], 'VariableNames',{'firstVariable'}, 'VariableTypes',{'double'})
myTable = 10×1 table
    firstVariable
    _____________

          0      
          0      
          0      
          0      
          0      
          0      
          0      
          0      
          0      
          0      
myTable.firstVariable = (1:numel(myTable.firstVariable)).'
myTable = 10×1 table
    firstVariable
    _____________

          1      
          2      
          3      
          4      
          5      
          6      
          7      
          8      
          9      
         10      

See Preallocate Table and Fill Rows for an extended discussion.

.

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Answer 2

Matt J 2021-11-29

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编辑：Matt J 2021-11-29

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I cannot use a struct or array. The datatype must remain as a table.

You cannot avoid wokring with arrays as an intermediary, however, the data does not have to remain as an array. You can convert it to a table, e.g.,

T=nan(5,10);
T(:,1)=1:5;
T=array2table(T)
T = 5×10 table
    T1    T2     T3     T4     T5     T6     T7     T8     T9     T10
    __    ___    ___    ___    ___    ___    ___    ___    ___    ___

    1     NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN
    2     NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN
    3     NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN
    4     NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN
    5     NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN    NaN