Extract Variable/column with variable name from table

Question

yvesvincent abgrall 2019-9-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480587-extract-variable-column-with-variable-name-from-table

编辑： Stephen23 2022-10-15

Hello,

I don't know how to extract a column with its variable name from a Matlab table.

I want to extract columns and not have to rename them afterwards in order to recreate a similar table bbut with only the column I want.

I need to extract them one at the time and the data types are different from one column to another.

I've tried different ways and read the matlab documentation but haven't found any solution.

Could you please help me? :)

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Answer 1

Steven Lord 2019-9-16

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https://ww2.mathworks.cn/matlabcentral/answers/480587-extract-variable-column-with-variable-name-from-table#answer_392079

编辑：Steven Lord 2019-9-16

在 MATLAB Online 中打开

In what form do you want the extracted variables to be stored?

A = magic(4);
T = array2table(A) % Variable names A1 through A4
smallerTable1 = T(:, {'A2', 'A4'}) % Smaller table with only two variables
smallerTable2 = T(:, [2 4]) % Smaller table with only two variables
vector1 = T.A2 % Double array, no variable names
vector2 = T{:, {'A2'}} % Double array, no variable names
vector3 = T{:, 2} % Double array, no variable names

If you want to process each variable from your table in turn, but you want to perform the same operation on each, consider using varfun.

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Dylan Gomes 2022-10-13

This is so clunky, is there really not a way to directly call vectors within a table in Matlab (like T.A2 or T$A2)?

Stephen23 2022-10-13

编辑：Stephen23 2022-10-15

"This is so clunky, is there really not a way to directly call vectors within a table in Matlab (like T.A2 or T$A2)?"

Here it is shown in Steven Lord's answer above:

Read more: https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-table.html

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Answer 2

Bob Thompson 2019-9-16

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https://ww2.mathworks.cn/matlabcentral/answers/480587-extract-variable-column-with-variable-name-from-table#answer_392075

I believe you can get this as a return.

T.Properties.VariableNames % T is the table variable

Additionally, because you're putting them into another table, if you just extract the specific columns you want the new table, and they will carry the variable names with them.

>> A = randi(100,10,4);
>> A = array2table(A);
>> A.Properties.VariableNames
ans =
  1×4 cell array
    {'A1'}    {'A2'}    {'A3'}    {'A4'}
    
>> B = A(:,[2,4]);
>> B.Properties.VariableNames
ans =
  1×2 cell array
    {'A2'}    {'A4'}

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yvesvincent abgrall 2019-9-16

Thank you for your answer Bob Nbob.

Using Properties.VariablesNames doesn't extract the data of the column.

I need to extract both the data and the variable name.

Bob Thompson 2019-9-16

As I mentioned, if you are extracting the column data into another table then the variable name will follow with it. Just put the information into a table class variable, which can be done most easily by indexing the portion of the original table that you want into a clean variable.

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