[R] problem merging data with different shapes

[Miriam]

I have been trying to merge datasets, one of which has a long format (Adata) and one has a (different) long format (Bdata):

Adata                              Bdata
subject order bpm                  subject order trial agegroup gender
1         1   70.2                    1      1     3       2       1
1         1   69.5                    1      2     1       2       1
1         1   68.8                    1      3     2       2       1    
1         2   69.1                    2      1     2       1       2
1         2    70                     2      2     3       1       2
1         2   70.5                    2      3     1       1       2
1         3   70.2                    ...
1         3    
1         3
2         1 
2         1 
...       ...

In the end I would like to have a dataset that contains A unchanged with the additional information from B added.

subject order bpm trial agegroup gender
1         1   70.2  3       2       1
1         1   69.5  3       2       1    
1         1   68.8  3       2       1    
...          
I have tried:
newdataframe <- merge(Adata,Bdata, by= c("subject", "order"), sort = FALSE)

For some reason, the trial column is not matched to the subject and order information, despite them being identified as key-variables for the merge. (The same is true for other variables, the actual dataset has more variables and trials, but this is essentially the problem.)
So it results in something like:
subject order bpm trial agegroup gender
1         1   70.2  3       2       1
1         1   69.5  2       2       1    
1         1   68.8  1       2       1 

What could be my mistake?

Thank you VERY much.
Miriam


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