Delete rows in data frame if entry appears fewer than x times

Question

I have the following data frame, call it df, which is a data frame consisting in three vectors: "Name," "Age," and "ZipCode."

df=      
  Name Age ZipCode
1  Joe  16   60559
2  Jim  20   60637
3  Bob  64   94127
4  Joe  23   94122
5  Bob  45   25462

I want to delete the entire row of df if the Name in it appears fewer than 2 times in the data frame as a whole (and flexibly 3, 4, or x times). Basically keep Bob and Joe in the data frame, but delete Jim. How can I do this?

I tried to turn it into a table:

> table(df$Name)

Bob Jim Joe 
 2   1   2

But I don't know where to go from there.

A5C1D2H2I1M1N2O1R2T1 · Accepted Answer · 2013-12-17T05:37:45.277

7

You can use ave like this:

df[as.numeric(ave(df$Name, df$Name, FUN=length)) >= 2, ]
#   Name Age ZipCode
# 1  Joe  16   60559
# 3  Bob  64   94127
# 4  Joe  23   94122
# 5  Bob  45   25462

This answer assumes that df$Name is a character vector, not a factor vector.

You can also continue with table as follows:

x <- table(df$Name)
df[df$Name %in% names(x[x >= 2]), ]
#   Name Age ZipCode
# 1  Joe  16   60559
# 3  Bob  64   94127
# 4  Joe  23   94122
# 5  Bob  45   25462

edited Dec 17 '13 at 05:37

answered Dec 17 '13 at 05:30

A5C1D2H2I1M1N2O1R2T1

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First one works, but the second one is exactly what I was looking for. Thanks so much! – Mon Dec 17 '13 at 05:46
@Mlee, No problem. You can also explore the "data.table" package, which will let you do things like: `library(data.table); DT <- data.table(df); DT[, count := .N, by = Name][count >= 2]`. – A5C1D2H2I1M1N2O1R2T1 Dec 17 '13 at 05:50
3

...or shorter data.table version, with credit to @mnel - `DT[, if(.N >= 2) .SD, by=Name]` – thelatemail Dec 17 '13 at 06:09
@thelatemail, nice one! – A5C1D2H2I1M1N2O1R2T1 Dec 17 '13 at 06:30

Delete rows in data frame if entry appears fewer than x times

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