Deleting specific rows from a data frame

Question

I am working with some US govt data which has a lengthy list of cities and zip codes. After some work, the data is in the following format.

dat1 = data.frame         


        

Answer 1

It helps to store the data as characters, not factors:

dat2 <- data.frame(keyword=c("Bremen", "Brent", "50143", "Chelsea, AL", 
                             "Bailytown, Alabama", "52348", "54023", "54024"),   
                   tag=c(rep("AlabamCity",2), rep("AlabamaCityST",2), 
                         rep("AlabamaCityState",2), rep("AlabamaZipCode",2)),
                   stringsAsFactors = FALSE) ## note this bit

Now we can convert keyword to numeric, and if it isn't a number in character format, we get an NA:

want <- with(dat2, as.numeric(keyword))

which gives us this:

> (want <- with(dat2, as.numeric(keyword)))
[1]    NA    NA 50143    NA    NA 52348 54023 54024
Warning message:
In eval(expr, envir, enclos) : NAs introduced by coercion

You can ignore the warning or suppress it, but don't use this casually as it can mask problems:

suppressWarnings(want <- with(dat2, as.numeric(keyword)))

The final step is to select the elements of want that are not NA and have keyword equal to "AlabamaZipCode", which we do using &:

(!is.na(want) & (dat2$tag != "AlabamaZipCode"))

That selects the rows we don't want, so we need to negate the above, turning TRUE to FALSE and vice versa:

!(!is.na(want) & (dat2$tag != "AlabamaZipCode"))

Putting this together we have:

dat2[!(!is.na(want) & (dat2$tag != "AlabamaZipCode")), ]

which gives:

> dat2[!(!is.na(want) & (dat2$tag != "AlabamaZipCode")), ]
             keyword              tag
1             Bremen       AlabamCity
2              Brent       AlabamCity
4        Chelsea, AL    AlabamaCityST
5 Bailytown, Alabama AlabamaCityState
7              54023   AlabamaZipCode
8              54024   AlabamaZipCode

Full solution is:

want <- with(dat2, as.numeric(keyword))
dat2[!(!is.na(want) & (dat2$tag != "AlabamaZipCode")), ]