CODEWITHSUNDEEP
r
Amateur
Amateur

Reputation: 1277

simple if else statement in syntax error in R

I would like to R to the following: if LocID is equal to 3,4,7,8, 14 then data$newConc is equal to data$conc/2 else data$newConc <- data$conc # else keep conc the same

data$newConc <- if(data$LocID == c(3,4,7,8,14))
data$conc/2 else data$conc

str(data)
 $ LocID     : int  1 2 3 4 5 6 7 8 9 10 ...
 $ time      : int  1 1 1 1 1 1 1 1 1 1 ...
$ conc      : num  0.03695 0.0155 0.00738 0.00753 0.01795 ...

Warning: the condition has length > 1 and only the first element will be used

Upvotes: 0

Views: 742

Answers (1)

mathematical.coffee
mathematical.coffee

Reputation: 56905

As far as I can tell from your code (which won't even run, due to a missing closing bracket?) you're trying to do (pseudocode):

foreach row in data
    if row$LocID is one of 3, 4, 7, 8, or 14
    THEN set row$newConc to row$conc/2
    ELSE set row$newConc to row$conc

To do this you use ifelse.

Also, if you want to test if a value is equal ot 3, 4, 7, 8 or 14, then don't use == -- that will return a vector of booleans, and if requires a single boolean, hence your error.

Either use data$locID %in% c(3,4,7,8,14) to return a single TRUE/FALSE, or use any(data$locID == c(3,4,7,8,14)) to turn the vector of booleans into a single boolean:

You're comparing a scalar to a vector, and so your output is a vector. An if statement only takes in a single boolean (not a vector of booleans).

Either use data$locID %in% c(3,4,7,8,14) to return a single TRUE/FALSE, or use any(data$locID == c(3,4,7,8,14)) to turn the vector of booleans into a single boolean:

data$newConc <- ifelse( data$locID %in% c(3,4,7,8,14),
                        data$conc/2,
                        data$conc )

Alternatively I could have used ifelse( any(data$locID == c(3,4,7,8,14)), ... ).

Upvotes: 5

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