MATLAB: Merge tables with different dimensions

table

Hi,

I'm trying to use vertcat to add together a sequence of tables. The problem is, some are 24×22, some are 24×19, 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.

Best Answer

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]

Related Solutions

MATLAB: Table variable name based on array

Do you mean like this:

c.(colnames{1}) = a; 
c.(colnames{2}) = b;

MATLAB: Merging CSV files with similar data structure into table

Bjorn, you can create a table with three variables, full of NaNs, and then just assign the variables you have read in from each csv. Something like this:

Create an example of a table that might have been read in using readtable:

>> t2 = array2table(randn(5,2),'VariableNames',{'height' 'color'})
t2 = 
     height      color 
    ________    _______
    -0.20497     0.6715
    -0.12414    -1.2075
      1.4897    0.71724
       1.409     1.6302
      1.4172    0.48889

Preallocate a table of missing values, with the right size:

>> t1 = array2table(nan(height(t2),3),'VariableNames',{'height' 'size' 'color'})
t1 = 
    height    size    color
    ______    ____    _____
    NaN       NaN     NaN  
    NaN       NaN     NaN  
    NaN       NaN     NaN  
    NaN       NaN     NaN  
    NaN       NaN     NaN

Move the data that was read in:

>> t1(:,t2.Properties.VariableNames) = t2
t1 = 
     height     size     color 
    ________    ____    _______
    -0.20497    NaN      0.6715
    -0.12414    NaN     -1.2075
      1.4897    NaN     0.71724
       1.409    NaN      1.6302
      1.4172    NaN     0.48889

Do that three times, and the three results can be vertically concatenated, Another possibility:

>> t2 = array2table(randn(5,2),'VariableNames',{'height' 'color'})
t2 = 
     height      color 
    ________    _______
      1.0347     0.8884
     0.72689    -1.1471
    -0.30344    -1.0689
     0.29387    -0.8095
    -0.78728    -2.9443
>> t2{:,setdiff({'height' 'size' 'color'},t2.Properties.VariableNames)} = NaN
t2 = 
     height      color      size
    ________    ________    ____
      1.4384    -0.10224    NaN 
     0.32519    -0.24145    NaN 
    -0.75493     0.31921    NaN 
      1.3703     0.31286    NaN 
     -1.7115    -0.86488    NaN

Best Answer

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MATLAB: Table variable name based on array

MATLAB: Merging CSV files with similar data structure into table

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