CODEWITHSUNDEEP
r
gersh
gersh

Reputation: 2437

How do I make an array of classes in R?

I'd like to put class objects into an array, so I can reference multiple class object. However, the class information seems to disappear when I put it into the array. How do I fix this?

Upvotes: 5

Views: 7188

Answers (2)

Sacha Epskamp
Sacha Epskamp

Reputation: 47642

I think you are misinterpreting the concept "array" in R. An array in R is not a vector of different objects but a multidimensional object with only elements of one class. A list is the R object that can be used to store whatever you want. If you want, you can even give it dimensions so you can get a multi-dimensional list, which would correspond to the array you describe. This must be indexed with double square brackets.

Example:

# A list with different objects:
foo <- list("A","B","C","D",1,2,3,4,TRUE,TRUE,FALSE,FALSE)

# Add dimensions:
dim(foo) <- c(2,2,3)
> foo
, , 1

     [,1] [,2]
[1,] "A"  "C" 
[2,] "B"  "D" 

, , 2

     [,1] [,2]
[1,] 1    3   
[2,] 2    4   

, , 3

     [,1] [,2] 
[1,] TRUE FALSE
[2,] TRUE FALSE

# index row 1 col 1 slice 1
> foo[[1,1,1]]
[1] "A"

Upvotes: 5

Gavin Simpson
Gavin Simpson

Reputation: 174948

Arrays aren't the right tool for this, as they are atomic (so allow only one basic type of data) and also allow only numeric or character data. A list is a generic vector in R and as such each component of a list can contain any type of object.

Here is an example for two user defined S3 classes:

> foo <- 1:10
> class(foo) <- "foo"
> bar <- "a"
> class(bar) <- "bar"
> 
> obj <- list(foo = foo, bar = bar)
> obj
$foo
 [1]  1  2  3  4  5  6  7  8  9 10
attr(,"class")
[1] "foo"

$bar
[1] "a"
attr(,"class")
[1] "bar"

Upvotes: 7

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