Why do I obtain an error about string cells when I try to join two datasets in MATLAB (R2013a)?

I am using the function JOIN on two datasets:

>> C = join(dataset1,dataset2);

but I obtain the following error:

 Error using dataset/join (line 274)

 Left and right key variables 'key1' and 'key1' include cells containing non-string values.

Answer 1

[MathWorks Support Team]

The reason behind the error is that the content of your dataset, under the variable name 'key1' must be of type 'char", and not "double", as in your case.

To circumvent this issue, you need to do a data-type conversion. Here is an example that illustrates that. Say, your variable name tagged "key1" is located in column "idx1" in "dataset1" and in column "idx2" in "dataset2".

>> varName1 = dataset1.Properties.VarNames(idx1);

>> cellData1  = dataset2cell(dataset1(:,idx1));

>> data1    = cellData1(2:end,2);

>> data1    = cellfun(@num2str,data1,'UniformOutput',false);

>> ds1      = dataset(data1,'Varnames',varName1,'ObsNames',dataset1.Properties.ObsNames);

>> dataset1(:,idx1) = ds1;

>> varName2 = StatSet.Properties.VarNames(idx2);

>> cellData2  = dataset2cell(dataset2(:,idx2));

>> data2    = cellData2(2:end,2);

>> data2    = cellfun(@num2str,data2,'UniformOutput',false);

>> ds2      = dataset(data2,'Varnames',varName2,'ObsNames',dataset2.Properties.ObsNames);

dataset2(:,idx2) = ds2;

C = join(dataset1,dataset2,'Key','key1');