CODEWITHSUNDEEP
rclass
user4704857
user4704857

Reputation: 469

Using default values in defined class in R

I am trying to define class which one of its slots is a list. The definition of my class is as follows:

setClass("myClass",
     slots=c(a="matrix", 
             b="matrix", 
             c="character", 
             d="list"))

d is a list of some parameters as follows:

d <- list(d1=c('as','sd'), d2=c(2,3,4), d3=5)

The number of elements in d is variable, i.e. in one object it may has just d1 and in another object it contains d1 and d2.

I want to define an object like this:

myObject=new("myClass", 
       a = matrix(0, nrow=3, ncol=5), 
       b=matrix(1, nrow=2, ncol=3), 
       c='first', 
       d=list(d1=c('ak','fd','sd'), d2=c(2,3,4)))

After defining myObject, I want to set d3 in list d to its default value, but I do not know how can I do that. I appreciate if anyone can help me.

Thanks.

Upvotes: 4

Views: 194

Answers (1)

Martin Morgan
Martin Morgan

Reputation: 46856

A class can be provided with a prototype

.myClass <- setClass("myClass",
     slots=c(a="matrix", 
             b="matrix", 
             c="character", 
             d="list"),
     prototype=prototype(
             d=list(d1=c('as','sd'), d2=c(2,3,4), d3=5)))

Code to use the prototype as a template updated by a variable d might be

d=list(d1=c('ak','fd','sd'), d2=c(2,3,4))
myd <- getClass("myClass")@prototype@d
myd[names(d)] <- d

The new class could be instantiated with

.myClass(d=myd)

One could expose this in a more user-friendly way by defining an initialize() method, or by writing a constructor, as

myClass <- function(a, b, c, d, ...) {
    myd <- getClass("myClass")@prototype@d
    myd[names(d)] <- d
    .myClass(a=a, b=b, c=c, d=myd, ...)
}

Having a list as a slot kind of defeats the purpose of using classes in the first place; maybe it's better to have explicit slots d1, d2, d3?

Upvotes: 2

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