Sam,
Depending on what your ultimate aim is, perhaps you just want to add
the 'drop=TRUE' argument to your interaction call.
Peter
Sam Player wrote:
#I have a dataset with two factor. I want to combine those factors into
a single factor and count the number of data values for each new factor.
The following gives a comparable dataframe:
a <- rep(c("a", "b"), c(6,6))
b <- rep(c("c", "d"), c(6,6))
df <- data.frame(f1=a, f2=b, d=rnorm(12))
df
# I use the 'interaction' function to combine factors f1 and f2:
df2 <- data.frame(f3=interaction(df[,"f1"], df[,"f2"]), d=df[,"d"])
df2
# A count of the first data.frame using factor f1 returns the kind of
results I am looking for:
count <- as.data.frame(table(df$f1))
count
# Var1 Freq
#1 a 6
#2 b 6
# As does a count using factor2:
count2 <- as.data.frame(table(df$f2))
count2
# Var1 Freq
#1 a 6
#2 b 6
# The same procedure on the second dataframe does not treat the levels
of factor f3 discreetly, instead giving all possible combinations of f1
and f2.
count3 <- as.data.frame(table(df2$f3))
count3
# Var1 Freq
#1 a.c 6
#2 b.c 0
#3 a.d 0
#4 b.d 6
I need the results to be:
# Var1 Freq
#1 a 6
#2 b 6
# Any suggestions?
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