Reshape data for values in one column

Question

My data.frame looks like this

ID | test | test_result
1  |  B   |   10
2  |  A   |   9
3  |  A   |   11
4  |  C   |   7
5  |  F   |   5

And

Answer 1

Another solution using reshape function in base R.

reshape(mydf, direction = 'wide', idvar = 'test', timevar = 'ID', 
  v.names = 'test_result', sep = "_")

EDIT. I see that you have already tried reshape and it took too long. Can you provide more details on your actual data?