Join Multiple Tables horizontally (can have duplicate variables) in which some tables might be empty.

Hello All,

I want to Join Multiple Tables horizontally (can have duplicate variables) in which some tables might be empty.

How to do that ?

TIA!!!

Answer 1

[Benjamin Kraus]

If your goal is to simply concatenate two tables, such that the first row of each table is combined into the first row of the output, the second row of each table is merged into the second row of the output, etc. all you need is to use the [] operator. That is, assuming they are the same height, or one of the tables is empty, and none of the tables have duplicate variable names. However, it is easy to fix duplicate variable names.

Consider this example:

t1 = table((1:10)')

t1 = 10×1 table
    Var1
    ____

      1 
      2 
      3 
      4 
      5 
      6 
      7 
      8 
      9 
     10 

t2 = table((11:20)')

t2 = 10×1 table
    Var1
    ____

     11 
     12 
     13 
     14 
     15 
     16 
     17 
     18 
     19 
     20 

t3 = table()

t3 =

  0×0 empty table

% Append a prefix to table variable names to avoid duplicate names.
t1.Properties.VariableNames = "t1." + t1.Properties.VariableNames

t1 = 10×1 table
    t1.Var1
    _______

       1   
       2   
       3   
       4   
       5   
       6   
       7   
       8   
       9   
      10   

t2.Properties.VariableNames = "t2." + t2.Properties.VariableNames

t2 = 10×1 table
    t2.Var1
    _______

      11   
      12   
      13   
      14   
      15   
      16   
      17   
      18   
      19   
      20   

% Now concatenate the three matrices:
t = [t1 t2 t3]

t = 10×2 table
    t1.Var1    t2.Var1
    _______    _______

       1         11   
       2         12   
       3         13   
       4         14   
       5         15   
       6         16   
       7         17   
       8         18   
       9         19   
      10         20   

If your goal is more of a "join" operation, in which you use the value in one variable of each table as a key to match rows from multiple tables, you want to look into the different ways to Join Tables, including the innerjoin, outerjoin, and join commands.