Concatenate cell with numeric array in tables

I have a ridiculously simple problem that I cannot solve. I have two tables and I want to concatenate them, but one contains a column with a cell array and one with a numeric array.

a = table([1; 2; 3]);
b = table({[1 2]; [3 4]})
c = [a; b];

This immediately produces an error because I am trying to concatenate a cell with a non-cell type. But if I just try to concatenate these variables outside a table, it works fine, recognizing that the result should be a cell array. There seems to be no way of telling matlab that I want it to convert a's variable to a cell array.

The actual problem is somewhat more complex - it's easy enough to solve this in the current case by just removing the variables from the table and concatenating them, then making a new table. But in the actual use case the tables have up to 50 variables, and it's unknown at runtime which of them are causing the problem.

Suggestions?

Answer 1

[Robert U]

Hi Marcus Watson,

an straight-forward solution would be checking the variable types stored in the table. In case they don't match change the numerical one to cell array.

a = table([1; 2; 3]);
b = table({[1 2]; [3 4]})

if ~cellfun(@isempty,{a{:,vartype('numeric')}}) && cellfun(@isempty,{b{:,vartype('numeric')}})
    a = table({a{:,vartype('numeric')}});
elseif cellfun(@isempty,{a{:,vartype('numeric')}}) && ~cellfun(@isempty,{b{:,vartype('numeric')}})
    b = table({b{:,vartype('numeric')}});
end

c = [a; b];

In case there are anyway no numerical values to concatenate you can change all tables that are containing numerical values to cells.

Kind regards,

Robert

[Marcus Watson]

That does at least allow the concatenation, which is a step in the right direction, but it converts A into a single cell in the resulting concatenated table (and the cell contains the vector). What I need is the ability to have every row of A and B be a row in C. Unfortunately I'm not sure that's possible without looping through each value, one at a time.

[Robert U]

How to deal with rows having a different number of columns?

I came accross the same wish while thinking about a solution. In your example a is 3x1 double whereas b is 2x2. What format is expected as output? Matlab does not even support that kind of concatenation with numerical data types.

Kind regards,

Robert

[Marcus Watson]

No, b is a 2x1 cell vector. So I’m hoping for the resulting concatenation to be a 5x1 cell.

[Robert U]

a = table([1; 2; 3]);
b = table({[1 2]; [3 4]});

if cellfun(@isempty,{a{:,vartype('cell')}}) && ~cellfun(@isempty,{b{:,vartype('cell')}})
    a = table(num2cell(a{:,vartype('numeric')}));
elseif ~cellfun(@isempty,{a{:,vartype('cell')}}) && cellfun(@isempty,{b{:,vartype('cell')}})
    b = table(num2cell(b{:,vartype('numeric')}));
end

c = [a; b];

[Marcus Watson]

Apologies my previous comment's code did not actually do the same as yours. Yours is the only one that I've seen work.