How to recode dot to NA in R?

user_13723763 0
Viewed 527

I have a data set where missing values have been coded with a dot. I would like to have missing values blank (NA).

Here is the data frame:

df <- data.frame(ITEM1 = c(6, 8, '.'),
                   ITEM2 = c(1, 6, 9),
                   ITEM3 = c(4, 2, 5),
                   ITEM4 = c('.', 3, 2),
                   ITEM5 = c(1, 6, 9)
)

df

ITEM1 ITEM2 ITEM3 ITEM4 ITEM5
1     6     1     4     .     1
2     8     6     2     3     6
3     .     9     5     2     9
>
na r
3 Answers

The columns will be character class because of the presence of .. Create a logical matrix with == and assign those elements to NA, then convert the data.frame columns to its appropriate type with type.convert

df[df == "." & !is.na(df)] <- NA
df <- type.convert(df, as.is = TRUE)

Or in a single step with replace (which internally does the assignment)

df <- type.convert(replace(df, df == "." & !is.na(df), NA), as.is = TRUE)

Or another approach is

df[] <- lapply(df, function(x) replace(x x %in% '.', NA))
df <- type.convert(df, as.is = TRUE)

Generally, this can be avoided all together, while reading the data itself i.e. specify na.strings = "." in read.csv/read.table etc.

user_37322710

You could use the na_if function from dplyr. Note that the dot changes the type of your columns to be char which might not be what you want afterwards! The following code finds all char columns, replaces . with NA and converts the column to be numeric:

df <- df %>%
    mutate(across(where(is.character), ~as.numeric(na_if(., "."))))
user_100308450

Here is an alternativ with set_na from sjlabelled package. Note the columns will remain as character type.

library(sjlabelled)
set_na(df, na = ".", as.tag = FALSE)

Output:

ITEM1 ITEM2 ITEM3 ITEM4 ITEM5
1     6     1     4  <NA>     1
2     8     6     2     3     6
3  <NA>     9     5     2     9
user_133216470
Related