On May 5, 2011, at 6:28 PM, J wrote:
Hi, I'm requesting you don't berate me for asking this question:
I clearly don't have the gist of factors.
I have two dataframes, A and B.
Each of them has a column containing strings (they're labels).
I want to, one-by-one in a loop, compare the particular string in an
entry from dataframe A to an entry in B, to see if they're the same.
The problem, when posing the question:
searchID1 <- A[['label']][i]
possMatch1 <- B[['label']][j]
searchID1 == possMatch1
I get the error:
Error in Ops.factor(searchID1, possMatch1) :
level sets of factors are different
I presume this is because the set of possible values in the 'labels'
columns, respectively in A and B, differ. In my case, I'm not
interested in this at all; I just want to compare individual entries
from the two dataframes in a pair-wise fashion.
Can I strip the "factors" associated with the entries? Is there a
better way?
Use as.character around the factors. Assuming they have equal nummbers
of rows, then no loop is needed:
searchID1 <- as.character(A[['label']])
possMatch1 <- as.character(B[['label']])
searchID1 == possMatch1 # returns pair-wise logical vector
And if the number of rows are not equal, then you need to express your
problem more clearly (and the dyadic function %in% is probably neededt)
--
David Winsemius, MD
West Hartford, CT
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