I have a function which looks at 9 different possibilities and chooses an action accordingly having the following form:
What I'm doing is looking up a vector and for each entry in the vector deciding
IF the value in the vector is 1 THEN start function B
IF the value in the vector is 2 THEN start function C
IF the value in the vector is 3 THEN start function D
IF the value in the vector is 4 THEN start function E
etc.
I would like to write this in R. Do I just put "else" for every single case?
I have tried switch
in the following way:
condition<-6
FUN<-function(condition){
switch(condition,
1 = random1(net)
2 = random2(net)
3 = random3(net)
4 = random4(net)
5 = random5(net)
6 = random6(net)
7 = random7(net)
8 = random8(net)
9 = random9(net)
10= random10(net))
}
Where random 1 to 10 are functions using the variable 'net'
and what the switch
command is trying to do is checking the value of 'condition' and if its 6 as in the above example then it runs the function: random6(net)
Both answers pointed you to the right tools, but this is IMHO how things ought to be written. The OP and both solutions so far are creating functions that use a global variable ( net
) which is not best practice.
Assuming randomX
are functions of one argument net
, ie:
random1 <- function(net){ [...] }
random2 <- function(net){ [...] }
[etc.]
Then you need to do:
FUN <- switch(condition,
'1' = random1,
'2' = random2,
[etc.])
or better:
FUN.list <- list(random1, random2, [etc.])
FUN <- FUN.list[[condition]]
In both cases, the output is a function that takes net
as an input (just like randomX
) so you can evaluate it by doing:
FUN(net)
Also note that you can do everything in one short scoop using the second approach:
FUN.list[[condition]](net)
Another solution is to pack all the functions you want to call into a list randoms
and then select a list item based on condition
:
randoms <- list(random1, random2, random3, random4, random5, random6, random7, random8, random9, random10)
FUN <- function(condition) {
randoms[[condition]](net)
}
Use switch
function as in:
foo <- function(condition){
switch(condition,
'1' = print('B'),
'2' = print('C'),
'3' = print('D'),
'4' = print('E'))
}
> foo(1)
[1] "B"
> foo(2)
[1] "C"
> foo(3)
[1] "D"
> foo(4)
[1] "E"
further details are in ?switch
based on your example:
condition<-6
FUN<-function(condition){
switch(condition,
'1' = random1(net), # Maybe you're missing some commas here
'2' = random2(net), # and here
'3' = random3(net), # and here
'4' = random4(net)
....) # all the way to '10' = random10(net)
}
this will do the trick
This works well for me:
Foo <- function(condition){
x <- 1:20
switch(condition,
'1' = mean(x),
'2' = var(x),
'3' = sd(x))
}
> Foo(1)
[1] 10.5
> Foo(2)
[1] 35
> Foo(3)
[1] 5.91608
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