[英]R: Create new Class offspring to “data.frame” with specific constructor
I am trying to create a new class in R for the first time and I have a hard time. 我想第一次在R中创建一个新类,我很难过。
Question 题
Can you please show me how one could create a class that inherits from the class "data.frame" but can only contain 3 columns named col1
, col2
and col3
. 你能否告诉我如何创建一个继承自“data.frame”类的类,但只能包含名为
col1
, col2
和col3
3列。 All columns must be "numeric" and the relation col1 + col2 = col3
must hold true. 所有列必须为“数字”,并且关系
col1 + col2 = col3
必须为true。
The user could do 用户可以这样做
ClassName(col1 = rep(10,10), col2 = 1:10)
or 要么
ClassName(col1 = rep(10,10), col3 = 11:20)
or 要么
ClassName(col2 = 1:10, col3 = 11:20)
to create an object of this class. 创建此类的对象。 All of the above lines would all yield to a similar output to
所有上述行都会产生类似的输出
data.frame(col1 = rep(10,10), col2 = 1:10, col3 = rep(10,10)+(1:10))
col1 col2 col3
1 10 1 11
2 10 2 12
3 10 3 13
4 10 4 14
5 10 5 15
6 10 6 16
7 10 7 17
8 10 8 18
9 10 9 19
10 10 10 20
What I tried 我尝试了什么
Here is all I manage to do so far. 这是我到目前为止所做的一切。
setClass("newClass", representation(col1="numeric",col2="numeric",col3="numeric"), contains="numeric")
calc.newClass = function(obj)
{
if (length(obj@col1)==0)
{
return(new("newClass", col1=obj@col3-obj@col2, col2=obj@col2, col3=obj@col3) )
}
if (length(obj@col2)==0)
{
return(new("newClass", col1=obj@col1, col2=obj@col3-obj@col1, col3=obj@col3) )
}
if (length(obj@col3)==0)
{
return(new("newClass", col1=obj@col1, col2=obj@col2, col3=obj@col1+obj@col2) )
}
}
o = calc.newClass(new("newClass", col1=rep(10,10), col3=11:20))
I failed to 我失败了
Maybe just do a S3 class: 也许只做一个S3类:
myclass <- function(col1, col2) {
if (missing(col2)) { stopifnot(is.numeric(col1)); col2 <- col1*2 }
if (missing(col1)) { stopifnot(is.numeric(col2)); col1 <- col2/2 }
structure(data.frame(col1, col2), class = c("myclass", "data.frame"))
}
(res <- myclass(col2=1:3))
# col1 col2
# 1 0.5 1
# 2 1.0 2
# 3 1.5 3
class(res)
# [1] "myclass" "data.frame"
(res <- myclass(col1=1:3))
# col1 col2
# 1 1 2
# 2 2 4
# 3 3 6
(res <- myclass(col1=letters[1:3]))
# Error: is.numeric(col1) ist nicht TRUE
(res <- myclass())
# Error in stopifnot(is.numeric(col1)) :
# argument "col1" is missing, with no default
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