Merge tables with different dimensions?

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Hi,
I'm trying to use vertcat to add together a sequence of tables. The problem is, some are 24x22, some are 24x19, etc.
Matlab returns the error
Error using table/vertcat (line 56)
All tables in the bracketed expression must have the same number
of variables.
Is there a way to work around this? Like, adding empty columns?
Thanks so much.

Accepted Answer

Guillaume
Guillaume on 19 Feb 2015
tables like matrices must have the same number of columns (variables with regards to tables) to concatenate them vertically. In addition, for tables, the variable names must be identical.
You can of course add variables to either table until all the variable names match:
t1 = array2table(magic(5), 'VariableNames', {'a', 'k', 'o', 'p', 'w'});
t2 = array2table(magic(6), 'VariableNames', {'a', 'p', 'o', 'v', 's', 'k'});
t1colmissing = setdiff(t2.Properties.VariableNames, t1.Properties.VariableNames);
t2colmissing = setdiff(t1.Properties.VariableNames, t2.Properties.VariableNames);
t1 = [t1 array2table(nan(height(t1), numel(t1colmissing)), 'VariableNames', t1colmissing)];
t2 = [t2 array2table(nan(height(t2), numel(t2colmissing)), 'VariableNames', t2colmissing)];
t = [t1; t2]
  6 Comments
Marguerite Kennish
Marguerite Kennish on 21 Aug 2020
I would like to repeat Ayana Cameron's question:
"How would this change to horizontally concatenate?"
I am trying to build a table by adding a column each iteration of a loop, but the rows of each column has different rows.

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More Answers (2)

Evan
Evan on 19 Feb 2015
Edited: Evan on 19 Feb 2015
Does this example do what you need?
A = randi(9,4,3)
B = randi(9,4,5)
C = randi(9,4,2)
D(1:4,1:size(A,2)) = A;
D(5:8,1:size(B,2)) = B;
D(9:12,1:size(C,2)) = C
You could then assign individual columns to new arrays which could be used as arguments to the table function. This would give you your zero padding for mismatched rows.
Note that if you are using the table function as sending in your arrays in the fashion
table(A,B,C)
you shouldn't receive errors so long as your variables all have an equal number of rows. It sounds like this isn't what you're doing, but without knowing exactly the way you want to arrange your data via some sample code, it's hard to say more.

Sterling Baird
Sterling Baird on 5 Sep 2020
Edited: Sterling Baird on 5 Sep 2020
I built on Guillaume's answer a while back, and recently ended up making and submitting a FEX function (tblvertcat) that supports cells in addition to other types which are supported by "missing" (double, char, etc.).
EDIT: I revamped the code to use outerjoin()

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