declaring a new table

Hi,

I would like to save data (that answer some conditions) from 2 different tables (T1, T2) to a new table (T3).

I tried to declare T3 and change the table's variable names but instead of a table, T3 is a structure.

T3.deltaY(r) = T2.y2(i) - T1.y1(j);

T3.x2(r) = T2.x2(i);

T3.x1(r) = T1.x1(j);

another question is how can I determine the size of the table in advanse instead of adding a new row at a time?

thanks!

Answer 1

[Bhaskar R]

After your opeartion, you can apply

T3 = struct2table(T3);    % converts from struct to table
[r, c] = size(T3);     % to find the size table

[sani]

Thanks!

I'm not sure this is what I meant. I want to avoid using structure at the first place, is there's a way I can initiate T3 size before writing into it?

Answer 2

[Stephen23]

For historic and compatibility reasons if the variable does not exist before the dot-indexing allocates to it, then MATLAB will initialize the variable as a structure:

>> clear
>> S.F = 1
S = 
    F: 1
>> class(S)
ans =
struct

If you want the variable to be a table then preallocate the table before the allocation:

>> T = table();
>> T.F = 1
T = 
    F
    _
    1
>> class(T)
ans =
table

[sani]

T3 = table();

T3.Properties.VariableNames{1} = 'deltaY';

T3.Properties.VariableNames{2} = 'x2';

T3.Properties.VariableNames{3} = 'x1';

for r = 1:height(T1(:,1))

for i = 1:height(T2(:,1))

T3.deltaY(r) = table2cell(T2.y2(i) - T1.y1(j));

T3.x2(r) = T2.x2(i);

T3.x1(r) = T1.x1(j);

end

end

I preallocate T3 as a table, but every time r edvanced a new row is addad in T3 which is very unefficient.