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nskel
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How do I add an additional column to a cell array based on existing values in another column?

Asked by nskel
on 12 Jun 2019
Latest activity Commented on by nskel
on 12 Jun 2019
I have a cell array (x) of dimensions 900x2. Column 1 is a unique identifier; there are two possible values of the second column, either "1" or "2". I want to add a third column which I want to be "1" if Column 2 is "1" and "0" otherwise.
I had previously asked a similar question where there were strings instead of numbers in Column 2 and a strcmp function was used but I would like to know similar function regarding numbers.
Any help appreciated!

  3 Comments

"1" is a string, '1' is a char or char vector, 1 is a number, either as single, double or an integer type. Instead of explaining the contents of the cell as text, prefer to use Matlab syntax, because then it is clear immediately:
x = {'asd', 1; ...
'bsd', 0};
% And you want to get:
y = {'asd', 1, 0; ...
'bsd', 0, 1};
Is this correct?
Yes, thanks! The second column contains integers.
Apologies!
... and yes that is the output I am looking for!

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3 Answers

Answer by Jan
on 12 Jun 2019
Edited by Jan
on 12 Jun 2019

x = {'asd', 1; ...
'bsd', 0};
x(:, 3) = num2cell(1 - cell2mat(x(:, 2)))
% or:
Value = {0, 1};
x(:, 3) = Value(2 - cell2mat(x(:, 2)))
This was one of the approaches for the char data:
Value = {'1', '0'};
x(:,3) = Value(2 - strcmp(x(:, 2), 'A'));
Here you can use the values to create the index instead of strcmp, but the equivalence is clear.

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Answer by Stephen Cobeldick on 12 Jun 2019

>> x = {'x1',1';'x2',2;'x3',1}
x =
'x1' [1]
'x2' [2]
'x3' [1]
>> x(:,3) = {0};
>> x([x{:,2}]==1,3) = {1}
x =
'x1' [1] [1]
'x2' [2] [0]
'x3' [1] [1]

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Answer by Joel Handy on 12 Jun 2019
Edited by Joel Handy on 12 Jun 2019

Obviously replace myCellArray with whatever your array is called.
isTwo = cellfun(@(x) x == 2, myCellArray(:,2));
myCellArray(:,3) = num2cell(double(isTwo))
Alternatively
isTwo = [myCellArray{:,2}]' == 2;
myCellArray(:,3) = num2cell(double(isTwo));
I'm not sure which is faster off hand.

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