Add table variable and assign constant string

Question

Bryan Wilson 2016-11-7

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https://ww2.mathworks.cn/matlabcentral/answers/311123-add-table-variable-and-assign-constant-string

评论： Peter Perkins 2016-11-10

I want to add a new variable to a table and assign a string to that variable for every row of the table.

T = table({'A';'B';'C'},[1;2;1],[6;7;5],...
    'VariableNames',{'Section' 'Data1' 'Data2'})
newString = "Project A"
T.newVar(:) = {newString}

T =

    Section    Data1    Data2      newVar  
    _______    _____    _____    __________
    'A'        1        6        [1x0 cell]
    'B'        2        7        [1x0 cell]
    'C'        1        5        [1x0 cell]

What I'd like is....T=

    Section    Data1    Data2      newVar  
    _______    _____    _____    __________
    'A'        1        6        'Project A'
    'B'        2        7        'Project A'
    'C'        1        5        'Project A'

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Answer 1

Walter Roberson 2016-11-7

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https://ww2.mathworks.cn/matlabcentral/answers/311123-add-table-variable-and-assign-constant-string#answer_242386

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T.newVar = repmat({newString}, size(T,1), 1)

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Guillaume 2016-11-7

编辑：Guillaume 2016-11-7

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Well, actually, if string means the new string type introduced in 2016b (as the double quotes would indicate), then:

T.newVar = repmat(string('Project A'), height(T), 1)

Bryan Wilson 2016-11-8

Typo - meant to use single quotes.

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Answer 2

Peter Perkins 2016-11-9

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https://ww2.mathworks.cn/matlabcentral/answers/311123-add-table-variable-and-assign-constant-string#answer_242664

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This slight change to the original code also works:

>> T.newVar(:,1) = newString % note the ",1"
T =
    Section    Data1    Data2      newVar   
    _______    _____    _____    ___________
    'A'        1        6        "Project A"
    'B'        2        7        "Project A"
    'C'        1        5        "Project A"

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Guillaume 2016-11-10

That is interesting. Is it documented anywhere?

It also does not make sense that one syntax works and the other doesn't since for a column vector (:) and (:, 1) should be exactly equivalent.

Peter Perkins 2016-11-10

Using (:,1) to create a new column vector is standard MATLAB syntax, and is sometimes needed to make sure your result becomes a column vector.

The issue here is that newVar doesn't yet exist as a column vector when you make the assignment. But in a table, it does seem like it shouldn't be needed. I will make a note to have that looked into.

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