MATLAB: Join tables by categorical variable

categoricaljoin;MATLABtable

I want to join two tables with indices of type categorical. However, I get an error.

I can convert both indices to string, then join, and then convert back to categorical again, but that seems ludicrous.

a = table(categorical(["a", "b", "c"]'), [1:3]')
b = table(categorical(["a", "b", "d"]'), [4:6]')
 
join(a,b,'Keys','Var1')

Gives "Left and right key variables 'Var1' and 'Var1' have incompatible types."

Best Answer

Turns out that my Matlab installation was corrupted, causing the mis-leading error message I received. After re-installation the error message changed and with using innerjoin instead of join on Akira's suggestion the code executed without errors. Thanks.

Related Solutions

MATLAB: Existing table, populate a column with string (receiving errors)

You are close, but you are trying to assign a character vector to a double variable (NaN = not a number). You can see that if you run the command summary(mytable).

You also do not need to put the text into a cell if you use the string data type.

See if you can get this code to work for your needs.

myArray = nan(5,2)
mytable = array2table(myArray);
mytable.Properties.VariableNames = {'colA', 'colB'};
mytable2 = convertvars(mytable,"colB",'string');
mytable2.colA(:) = 459;
mytable2.colB(:) = "words"

You say you have a lot of data. If the variables already exist, you could do something like this:

colA = nan(5,1);
colB = strings(5,1);
mytable = table(colA,colB);
mytable.colA(:) = 459; % just a random number, proof-of-concept that it works
mytable.colB(:) = "words" % this throws errors

MATLAB: Inner join two tables treating NaN entries as identical

Replace the NaNs with "inf", join the tables, then replace the inf with Nan.

% Change NaNs to Infs
A.Key2(isnan(A.Key2)) = inf;
B.Key2(isnan(B.Key2)) = inf;
AB = innerjoin(A,B);
% Replace Inf with nan
AB.Key2(isinf(AB.Key2)) = nan;

Result

AB =
  4×4 table 
    Key1    Key2    Var1    Var2
    ____    ____    ____    ____
    'a'     123      4       1  
    'b'     456      5       2  
    'd'     789      6       3  
    'e'     NaN      7       4

Best Answer

Related Solutions

MATLAB: Existing table, populate a column with string (receiving errors)

MATLAB: Inner join two tables treating NaN entries as identical

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