How do I assign a value to a particular column in a subsection of a table?

Asked by Karen on 9 May 2017

Latest activity Commented on by Peter Perkins on 10 May 2017

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Using the example testing data on https://www.mathworks.com/help/matlab/matlab_prog/calculations-on-tables.html, I would like to write something like

T(T.Gender=='female',:).Test2 = 100

I can do something similar with array data, but get an error with table data. Is there a simple way to make this work without having to create a dummy array of the appropriate length for my constant value?

    T = readtable(fullfile(matlabroot,'examples','matlab','testScores.csv'),...
                  'ReadRowNames',true)
    T.Gender = categorical(T.Gender)
    % select a subset of the rows
    rows = T.Gender=='female'
    % this works, and is my usual way of working with array data
    A = table2array(T(:,2:4))
    A(rows,2) = 100
    % This works, but is ugly
    T(rows,:).Test2 = 100 * ones(size(T(rows,:).Test2))
    % This does not work  
    T(rows,:).Test2 = 100

Error: 'To assign to or create a variable in a table, the number of rows must match the height of the table. '

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Answer by Walter Roberson on 9 May 2017

Accepted Answer

T{rows,'Test2'} = 100;

2 Comments

Karen on 9 May 2017

Thanks. After posting the question, I finally found the right page of documentation...

Peter Perkins on 10 May 2017

For assigning to just one variable in a table, you might find

T.Test2(rows) = 100;

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