CODEWITHSUNDEEP
r
Ed G
Ed G

Reputation: 822

Return an object from a function

How do I return an object from a function, rather than the output provided when you call the object?

best.mod <- function(d){
  m1 <- lm(Sepal.Length~Sepal.Width, d)
  m2 <- lm(Sepal.Length~Sepal.Width + I(Sepal.Width^2), d)
  ifelse(AIC(m1) < AIC(m2), m1, m2)
}

mod <- best.mod(iris[iris$Species == "setosa",])
class(mod)

Upvotes: 3

Views: 107

Answers (2)

James
James

Reputation: 66834

The problem comes from using ifelse. This is meant for vectorised comparisons. A standard if ... else is better here:

best.mod <- function(d){
  m1 <- lm(Sepal.Length~Sepal.Width, d)
  m2 <- lm(Sepal.Length~Sepal.Width + I(Sepal.Width^2), d)
  if(AIC(m1) < AIC(m2)) return(m1) else return(m2)
}

mod <- best.mod(iris[iris$Species == "setosa",])
class(mod)
[1] "lm"

Note the warning from ?ifelse:

The mode of the result may depend on the value of test (see the examples), and the class attribute (see oldClass) of the result is taken from test and may be inappropriate for the values selected from yes and no.

Upvotes: 5

Paul Hiemstra
Paul Hiemstra

Reputation: 60924

ifelse is not really meant for this kind of usage, simply use if and else for this:

best.mod <- function(d){
  m1 <- lm(Sepal.Length~Sepal.Width, d)
  m2 <- lm(Sepal.Length~Sepal.Width + I(Sepal.Width^2), d)
  if(AIC(m1) < AIC(m2)) m1 else m2
}

mod <- best.mod(iris[iris$Species == "setosa",])
class(mod)

ifelse is meant for this kind of things:

vec = runif(100)
ifelse(vec < 0.5, NA, vec)

Upvotes: 3

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