R: Count and convert to number

I have a dataframe with the following format.

A    B
xxx 100;2;30;5
yyy 30;5
zzz 35

How to count the number of numbers in column B in second column and convert to the count as follows:

A    B
xxx  4
yyy  2
zzz  1

Thank开发者_Python百科s.

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Assuming your data are in a data.frame named Data, a combination of strsplit and sapply make short work of this.

Data$C <- sapply(strsplit(Data$B, ";"), length)

strsplit is vectorized, so it splits each element of column Data$B by ";" and returns a list of vectors. The list has one element for each row in Data and each list element contains a vector (e.g. "100;2;30;5" is converted to c("100","2","30","5")). The sapply call returns the length of each vector in the list.

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This does the trick:

dfr$B<-nchar(as.character(dfr$B))-nchar(gsub(";","",dfr$B))+1

Edit: I think this should be slightly faster:

dfr$B<-nchar(as.character(dfr$B))-nchar(gsub(";","",dfr$B, fixed=TRUE))+1