Keep specific column variables and delete others?

Question

Tyla Ono 2018-8-18

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/415354-keep-specific-column-variables-and-delete-others

评论： Walter Roberson 2023-4-1

Hi, I have a table with a list of column variables (Eg: [[Var1 Var2 Var3 Var4 VarN]. I am trying to keep only specific variables and associated column data, whilst deleting all others.

For example, I want only variable 2 and 4, while deleting all other columns. Desired output --> [Var2 Var4]

It is possible to output only the desired columns without individually deleting unwanted variables?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Paolo 2018-8-18

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/415354-keep-specific-column-variables-and-delete-others#answer_333242

在 MATLAB Online 中打开

Var1 = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'};
Var2 = [38;43;38;40;49];
Var3 = logical([1;0;1;0;1]);
T = table(Var1,Var2,Var3)

To keep columns one and three:

T = [T(:,1) T(:,3)]
T =
    5×2 table
        Var1       Var3 
      _________    _____
      'Sanchez'    true 
      'Johnson'    false
      'Li'         true 
      'Diaz'       false
      'Brown'      true

Adapt the code for columns 2 and 4.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Tyla Ono 2018-8-19

Thank you.

请先登录，再进行评论。

Answer 2

Alex Whiteway 2022-5-19

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/415354-keep-specific-column-variables-and-delete-others#answer_967490

在 MATLAB Online 中打开

I know this is a bit old, but I wanted to put my preferred method using column names:

Var1 = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'};
Var2 = [38;43;38;40;49];
Var3 = logical([1;0;1;0;1]);
T = table(Var1,Var2,Var3)
%Keep just Var1 and Var3
Tnew = T(:,{'Var1', 'Var3'});

2 个评论
显示无隐藏无

Walter Roberson 2023-4-1

Nariman Mahmoudi comments to @Alex Whiteway

"much more efficient"

Walter Roberson 2023-4-1

在 MATLAB Online 中打开

Testing efficiency:

Var1 = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'};
Var2 = [38;43;38;40;49];
Var3 = logical([1;0;1;0;1]);
T = table(Var1,Var2,Var3)
T = 5×3 table
       Var1        Var2    Var3 
    ___________    ____    _____

    {'Sanchez'}     38     true 
    {'Johnson'}     43     false
    {'Li'     }     38     true 
    {'Diaz'   }     40     false
    {'Brown'  }     49     true 
%Keep just Var1 and Var3
tic; Tnew1 = T(:,{'Var1', 'Var3'}); toc
Elapsed time is 0.009980 seconds.
tic; Tnew2 = T(:,[1 3]); toc
Elapsed time is 0.006850 seconds.
tic; Tnew3 = [T(:,1), T(:,3)]; toc
Elapsed time is 0.037788 seconds.

So the {'Var1', 'Var3'} version is considerably more efficient than the [T(:,1), T(:,3)] option -- but it is not as efficient as indexing by variable numbers.

请先登录，再进行评论。