add new row to table with missing values

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Amirali Kamalian 2022-1-18

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https://ww2.mathworks.cn/matlabcentral/answers/1630980-add-new-row-to-table-with-missing-values

评论： KSSV 2022-1-18

How can I add a new row to an existing table with missing values?

For illustration, I define a table T with 4 variables: name, city, age, height.

V.name = "Ann";
V.city = "Berlin";
V.age = 24;
V.height = 172;
T = struct2table(V);

Now, I want to add another row to this table where the new row only contains values for 3 of the variables (out of 4).

V2.name = "Luka";
V2.city = "Tokyo";
V2.age = 30;
T = [T; struct2table(V2)];
All tables being vertically concatenated must have the same number of variables.

This leads to the following error:

"All tables being vertically concatenated must have the same number of variables."

What's the best practice for such situations?

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Answer 1

KSSV 2022-1-18

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https://ww2.mathworks.cn/matlabcentral/answers/1630980-add-new-row-to-table-with-missing-values#answer_876570

在 MATLAB Online 中打开

V.name = "Ann";
V.city = "Berlin";
V.age = 24;
V.height = 172;
T1 = struct2table(V);
V2.name = "Luka";
V2.city = "Tokyo";
V2.age = 30;
T2 = struct2table(V2);
T2.height = NaN ;
T = [T1;T2]
T = 2×4 table
     name       city      age    height
    ______    ________    ___    ______

    "Ann"     "Berlin"    24      172  
    "Luka"    "Tokyo"     30      NaN  

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Amirali Kamalian 2022-1-18

In each sequence of a for loop, a new row is added to the table. The values for the new row are collected in a struct and then struct2table is called to update the table with a new row.

Are you suggesting to collect all the data in a struct array and then convert that to a table in a single struct2table call? Does that give more flexibility in terms of "missing" values?

KSSV 2022-1-18

在 MATLAB Online 中打开

YEs exactly. That makes your life very easy.

V = struct ; 
V(1).name = "Ann";
V(1).city = "Berlin";
V(1).age = 24;
V(1).height = 172;
V(2).name = "Luka";
V(2).city = "Tokyo";
V(2).age = 30;
T = struct2table(V)
T = 2×4 table
     name       city      age       height   
    ______    ________    ___    ____________

    "Ann"     "Berlin"    24     {[     172]}
    "Luka"    "Tokyo"     30     {0×0 double}