Dear R users,
A co-worker and I are writing a function to facilitate graph plotting in R. The
function makes use of a lot of lists in its defaults.
However, we discovered that R does not necessarily preserve the defaults if we
were to input them in the form of list() when initializing the function. For
example, if you feed the function codes below into R:
myfunction=function(
list1=list (variable1=1,
variable2=2,
variable3=3),
list2=list (variable1="variable1",
variable2="variable2",
variable3="variable3"),
list3=list (variable1="character",
variable2=24,
variable3=c(0.1,0.1,0.1,0.1),
variable4=TRUE))
{return(list(list1=list1,list2=list2,list3=list3))}
By definition, the values associated with each variable in the lists would be
the default unless the user impute a different value while executing the
function. But a problem arises when a variable in the list is left out
completely (not imputed at all). An example is shown below:
myfunction( list1=list (variable1=1,
variable2=2), #variable 3 deliberately left out
list2=list (variable1="variable1",
variable3="position changed",
variable2="variable2"),
list3=list (variable1="character",
variable2=24,
variable4=FALSE)) #variable 3 deliberately left out
#The outcome of the above execution is shown below:
$list1
$list1$variable1
[1] 1
$list1$variable2
[1] 2
#list1$variable3 is missing. Defaults in function not assigned in this execution
$list2
$list2$variable1
[1] "variable1"
$list2$variable3
[1] "position changed"
$list2$variable2
[1] "variable2"
$list3
$list3$variable1
[1] "character"
$list3$variable2
[1] 24
$list3$variable4
[1] FALSE
#list3$variable3 is missing. Defaults in function not assigned in this execution
We later realized that the problem lies in list() commands. Hence, we tried to
enforce the defaults on the list using these codes in the function definition:
myfunction.alternative=function(
list1=list (variable1=1,
variable2=2,
variable3=3),
list2=list (variable1="variable1",
variable2="variable2",
variable3="variable3"),
list3=list (variable1="character",
variable2=24,
variable3=c(0.1,0.1,0.1,0.1),
variable4=TRUE))
{
defaults=vector("list", 3)
names(defaults)=c("list1","list2","list3")
defaults$list1=list(variable1=1,
variable2=2,
variable3=3)
defaults$list2=list(variable1="variable1",
variable2="variable2",
variable3="variable3")
defaults$list3=list (variable1="character",
variable2=24,
variable3=c(0.1,0.1,0.1,0.1),
variable4=TRUE)
if(length(list1$variable1)==0){list1$variable1=defaults$list1$variable1}
if(length(list1$variable2)==0){list1$variable2=defaults$list1$variable2}
if(length(list1$variable3)==0){list1$variable3=defaults$list1$variable3}
if(length(list2$variable1)==0){list2$variable1=defaults$list2$variable1}
if(length(list2$variable2)==0){list2$variable2=defaults$list2$variable2}
if(length(list2$variable3)==0){list2$variable3=defaults$list2$variable3}
if(length(list3$variable1)==0){list3$variable1=defaults$list3$variable1}
if(length(list3$variable2)==0){list3$variable2=defaults$list3$variable2}
if(length(list3$variable3)==0){list3$variable3=defaults$list3$variable3}
if(length(list3$variable4)==0){list3$variable4=defaults$list3$variable4}
return(list(list1=list1,list2=list2,list3=list3))}
The outcome of execution the above function with the same commands produces the
results that we wanted:
> myfunction.alternative( list1=list (variable1=1,
+ variable2=2), #variable 3 deliberately left out
+
+ list2=list (variable1="variable1",
+ variable3="position changed",
+ variable2="variable2"),
+
+ list3=list (variable1="character",
+ variable2=24,
+ variable4=FALSE)) #variable 3 deliberately left out
$list1
$list1$variable1
[1] 1
$list1$variable2
[1] 2
$list1$variable3
[1] 3
#list1$variable3 is assigned default despite being left out in the execution
command
$list2
$list2$variable1
[1] "variable1"
$list2$variable3
[1] "position changed"
$list2$variable2
[1] "variable2"
$list3
$list3$variable1
[1] "character"
$list3$variable2
[1] 24
$list3$variable4
[1] FALSE
$list3$variable3
[1] 0.1 0.1 0.1 0.1
#list3$variable3 is assigned default despite being left out in the execution
command
Even though the function works, as you can see, the codes that enforce the
defaults are very long and bulky. Such lengthy codes won't be efficient if we
have a write a function containing a large number of lists. We tried to come up
with ideas to try to shorten the codes, but so far none of them prove to be
effective.
What would be your recommendation to deal with such situation? It would be
great if you would be able to help us our with this problem. We appreciate your
help tremendously.
Thank you.
Sincerely,
Shang
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