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In the data frame, column A is expected to be a numeric vector.
So if an entry of the column has any non-numeric characters, I would remove the corresponding entire row.
Does anyone have a solution? Thanks!
680
To remove all rows having NA, we can use na. omit function. For Example, if we have a data frame called df that contains some NA values then we can remove all rows that contains at least one NA by using the command na. omit(df).
To remove a character in an R data frame column, we can use gsub function which will replace the character with blank. For example, if we have a data frame called df that contains a character column say x which has a character ID in each value then it can be removed by using the command gsub("ID","",as.
First of all, create a data frame. Then, use single square subsetting with apply function to remove rows that contains a specific number.
In order to remove all non-numeric characters from a string, replace() function is used. replace() Function: This function searches a string for a specific value, or a RegExp, and returns a new string where the replacement is done.
When you import data to a data.frame, it generally gets converted to a factor if the entire column is not numeric. With that in mind, you usually have to convert to character and then to numeric.
dat <- data.frame(A=c(letters[1:5],1:5))
str(dat)
'data.frame': 10 obs. of 1 variable:
$ A: Factor w/ 10 levels "1","2","3","4",..: 6 7 8 9 10 1 2 3 4 5
as.numeric(as.character(dat$A))
[1] NA NA NA NA NA 1 2 3 4 5
Warning message:
NAs introduced by coercion
Notice that it converts characters to NA. Combining this:
dat <- dat[!is.na(as.numeric(as.character(dat$A))),]
In words, the rows of dat that are not NA after conversion from factor to numeric.
Second Issue:
> dat <- data.frame(A=c(letters[1:5],1:5))
> dat <- dat[!is.na(as.numeric(as.character(dat$A))),]
Warning message:
In `[.data.frame`(dat, !is.na(as.numeric(as.character(dat$A))), :
NAs introduced by coercion
> dat <- dat[!is.na(as.numeric(as.character(dat$A))),]
Error in dat$A : $ operator is invalid for atomic vectors
Or using @Brandon Bertelsen's example data
dat1 <- transform(dat[grep("^\\d+$", dat$A),,drop=F], A= as.numeric(as.character(A)))
dat1
# A
#6 1
#7 2
#8 3
#9 4
#10 5
str(dat1)
#'data.frame': 5 obs. of 1 variable:
#$ A: num 1 2 3 4 5
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