Access table using logical array

Question

TrickyHeron 2024-1-2

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2065816-access-table-using-logical-array

评论： TrickyHeron 2024-1-2

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Is there a better way to index a table using a logical array?

Code to reproduce my issue:

Acol = [1; 2; 3; 4; 5; 6];
Bcol = [1; 2; 3; 4; 5; 6];
Ccol = [1; 2; 3; 4; 5; 6];
dataArray = [Acol Bcol Ccol];
mask1 = dataArray == 5;
dataArray(mask1) = nan; % do something to all 5s in the table
dataTable = table(Acol,Bcol,Ccol);
mask = dataTable == 5;
mask = table2array(mask);
dataTable(mask) = nan % error

The error is "Error using () Subscripting into a table using one subscript (as in t(i)) is not supported. Specify a row subscript and a variable subscript, as in t(rows,vars). To select variables, use t(:,i) or for one variable t.(i). To select rows, use t(i,:)."

Reading the documentation for table data access indicates that logical indexing is possible if I have a mask vector and use it for either the rows or columns of dataTable. For instance I get no errors doing the following:

mask = dataTable.Acol == 5;
dataTable(mask,:) % returns the row corresponding to the mask

However, I would like to logically index a table as I would for an array. I can do this if I first convert the table to an array, logically index, and then convert the array back to a table:

namesCell = dataTable.Properties.VariableNames;
dataTable = table2array(dataTable)
mask = dataTable == 5;
dataTable(mask) = nan;
dataTable = array2table(dataTable,'VariableNames',namesCell);

Is there a more efficient/ergonomic way to do this?

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Answer 1

Walter Roberson 2024-1-2

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2065816-access-table-using-logical-array#answer_1381896

在 MATLAB Online 中打开

Acol = [1; 2; 3; 4; 5; 6];
Bcol = [1; 2; 3; 4; 5; 6];
Ccol = [1; 2; 3; 4; 5; 6];
dataTable = table(Acol,Bcol,Ccol);
dataTable = standardizeMissing(dataTable, 5)
dataTable = 6×3 table
    Acol    Bcol    Ccol
    ____    ____    ____

      1       1       1 
      2       2       2 
      3       3       3 
      4       4       4 
    NaN     NaN     NaN 
      6       6       6 