[R] unique mismatch in R and Excel

[Koushik Saha]

i have a wired problem. i want to count the unique entry in a certain
column.Here i have attached my csv file.

i am doing this to get the unique entries in the column.

dat<-read.csv("C:/Project/Gawk-scripts/Book1.csv")
names(dat)<-c("user_name")
unique(dat$user_name)

results says i have 170 unique values.


But i am doing "remove duplicate entries"  in excel i am having 147 unique
entries in the column.

Can anyone explain why there is a mismatch of the results or i am doing
something wrong.

Regards
Koushik