In table, how to select values in one column based on values in another column?

Question

Doheon Lee 2021-4-17

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https://ww2.mathworks.cn/matlabcentral/answers/804911-in-table-how-to-select-values-in-one-column-based-on-values-in-another-column

评论： Doheon Lee 2021-4-20

As given in the title, I like to call values in one table based on values in anothe column. I have a follwoing table.

T = table({'a'; 'b'; 'c'; 'd'; 'e'}, [1;2;3;4;5], 'variablenames', {'name', 'value'});

I like to call elements in the 'value' column, for 'd', 'b', 'e' in the 'name' column. So the expected result is as below

I can do this with the following codes.

order = {'d', 'b', 'e'};
 
[Lia, Locb] = ismember(T.name, order);
order_chosen = T.value(Lia);
 
Locb = nonzeros(Locb);
result = order_chosen(Locb);

However, as you can see, lines seem too many for such a relatively simple outcome. So I wonder if there is way to do the samething efficiently with shorter lines.

Thank you for any help in advance.

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Answer 1

Cris LaPierre 2021-4-17

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The simplest way to do this is using logical indexing, but that doesn't preserve the order. That makes it a more challenging problem to solve. Still, it can be done in fewer lines. I suggest using find.

T = table({'a'; 'b'; 'c'; 'd'; 'e'}, [1;2;3;4;5], 'variablenames', {'name', 'value'});
% Find rows corresponding to names, preserving order
[rows,~]=find(T.name==["d","b","e"]);
result = T(rows,"value")
result = 3×1 table
    value
    _____

      4  
      2  
      5  