Ignore NAs so that I can add value to negative numbers

Question

I have a column that is the number of hours slept which was created by subtracting a wake_up column from the went_to_slepp columne - however, I am getting negative numbers because difftime is not recognizing that the PM values are for the first day and AM numbers are for the following day.

I realized that, mathematically, I come out with the correct number of hours if I can add 24 to the negative values.

However, because I have NA values I can only replace the negative values with 0 or NA and am getting an error when I try to add 24.

Example:

df$hours_slept[df$hours_slept < 0] <- d5_df$hours_slept + 24 

This gives me the error:

Error in NextMethod("[<-"): NAs are not allowed in subscripted assignments

I tried adding.is.na but that did not work in the way I thought it would

Thanks

Answer 1

You could use ifelse like so:

set.seed(1234)
df <- data.frame(hours_slept = sample(seq(-12,12, .1),20, replace=TRUE))
df$hours_slept[sample(1:20,8)] <- NA
df
#>    hours_slept
#> 1         -9.3
#> 2         -4.1
#> 3           NA
#> 4           NA
#> 5         11.5
#> 6         -1.0
#> 7          1.6
#> 8           NA
#> 9          4.5
#> 10          NA
#> 11         1.1
#> 12        -2.3
#> 13          NA
#> 14         9.3
#> 15          NA
#> 16        -5.1
#> 17        -4.2
#> 18         8.5
#> 19          NA
#> 20          NA
df <- transform(df, hours_slept=ifelse(hours_slept < 0, -hours_slept, hours_slept))
df
#>    hours_slept
#> 1          9.3
#> 2          4.1
#> 3           NA
#> 4           NA
#> 5         11.5
#> 6          1.0
#> 7          1.6
#> 8           NA
#> 9          4.5
#> 10          NA
#> 11         1.1
#> 12         2.3
#> 13          NA
#> 14         9.3
#> 15          NA
#> 16         5.1
#> 17         4.2
#> 18         8.5
#> 19          NA
#> 20          NA

^{Created on 2022-07-26 by the reprex package (v2.0.1)}