if statement with three outcomes - r

Question

I'd like to make a new column in which the value depends on other columns.
There are three possible outcomes
Distance < Min_disp = 0
Distance < Max_disp = Distance
Distance > Max_disp = Max_disp
I have tried using an if-statement, with multiple outcomes, but receive a warning.
Warning messages:
1: In if (Noord_2015_moved$Distance < Noord_2015_moved$Min_disp) { :
the condition has length > 1 and only the first element will be used
2: In if (Noord_2015_moved$Distance < Noord_2015_moved$Max_disp) { :
the condition has length > 1 and only the first element will be used
And indeed it only prints "Max_disp".
This is the code I've used
if (Noord_2015_moved$Distance < Noord_2015_moved$Min_disp) {
0
} else if (Noord_2015_moved$Distance < Noord_2015_moved$Max_disp) {
Noord_2015_moved$Distance
} else {
Noord_2015_moved$Max_disp
}
I have also tried running it in three separate steps, but then I run into the problem that I don't know how to tell R to only apply part of the df$column, because now I get the error
number of items to replace is not a multiple of replacement length
Noord_2015_moved <- mutate(Noord_2015_moved, Actual_disp = ifelse(Distance < Min_disp, 0, NA))
Noord_2015_moved$Actual_disp[Noord_2015_moved$Distance < Noord_2015_moved$Max_disp] <- Noord_2015_moved$Distance
Noord_2015_moved$Actual_disp[is.na(Noord_2015$Actual_disp)] <- Noord_2015_moved$Max_disp
And this is my data
'data.frame': 301 obs. of 15 variables:
$ Transmitter: Factor w/ 18 levels "A69-1601-22313",..: 1 1 1 1 1 1 1 2 2 2 ...
$ Date : Date, format: "2015-03-03" "2015-03-08" "2015-03-11" "2015-05-18" ...
$ Date_time : Factor w/ 279544 levels "1-03-15 0:00",..: 198302 258702 18684 85140 190788 182641 208718 26315 198759 205744 ...
$ Receiver : Factor w/ 17 levels "uitzetpunt 1-noord",..: 8 5 8 5 6 7 6 8 5 8 ...
$ Station : Factor w/ 17 levels "10","11","12",..: 15 12 15 12 13 14 13 15 12 15 ...
$ Traject : Factor w/ 53 levels "","10-10","10-9",..: 53 50 41 50 40 44 45 53 50 41 ...
$ Interval : num 83.4 12.7 42.6 25.2 217.4 ...
$ Distance : num 1540 6480 6480 6480 4690 4220 4220 1540 6480 6480 ...
$ Min_speed : num 0.02 0.51 0.15 0.26 0.02 0.73 0.52 0.01 0.02 0.02 ...
$ Min_speed2 : num 0.00556 0.14167 0.04167 0.07222 0.00556 ...
$ Length : int 47 47 47 47 47 47 47 45 45 45 ...
$ Activity : chr "Low" "Low" "Low" "Low" ...
$ Moved : chr "Yes" "Yes" "Yes" "Yes" ...
$ Min_disp : num 160 4080 1200 2080 160 5840 4160 80 160 160 ...
$ Max_disp : num 240 6120 1800 3120 240 8760 6240 120 240 240 ...

Answer 1

if() isn't vectorized. It work on a single condition, not a whole vector. That's what the warning "the condition has length > 1 and only the first element will be used" is telling you. You could use if() for this purpose, but you would need to put it in a for loop to check each row one-at-a-time. Doable, but not efficient.
ifelseis a vectorized version of if, and is good for a problem like this. For something like this, you would probably nest 2 ifelses:
Noord_2015_moved$Actual_disp = ifelse(
Noord_2015_moved$Distance < Noord_2015_moved$Min_disp, 0,
ifelse(Noord_2015_moved$Distance < Noord_2015_moved$Max_disp, Noord_2015_moved$Distance,
Noord_2015_moved$Max_disp
))
I see you have a single mutate. If you're using dplyr, you can use mutate which adds a column to the data frame and means you don't need to type out the data frame's name to reference existing columns. This code is equivalent to my above code:
Noord_2015_moved = Noord_2015_moved %>% mutate(
Acutal_disp = ifelse(Distance < Min_disp, 0,
ifelse(Distance < Max_disp, Distance, Max_disp)
)
)

Answer 2

In addition to using to ifelse multiple times, you can use dplyr::case_when, which handles multiple outcomes in the cleanest possible way:
Noord_2015_moved = Noord_2015_moved %>% mutate(
Acutal_disp = case_when(
Distance < Min_disp ~ 0,
Distance < Max_disp ~ Distance,
Distance > Max_disp ~ Max_disp,
TRUE ~ NA_real_
)
)
Here is a short reference.