I’m parsing some JSON data in R and got this structure:
entry <- list("Ontario"="ON", "ON"="13.6")
When I try:
j <- entry["Ontario"]
population <- as.numeric(entry[j])
I get an error:
Error in if (population > 0) { : argument is of length zero
I think I’m not accessing the element correctly. What is the right way to get "13.6" as a number?
[] returns a subset of your list, so a list object. You want [[]], which returns a single element/value:
entry <- list("Ontario"="ON", "ON"="13.6")
# Returns subset of your list (a list object)
entry["Ontario"]
# $Ontario
# [1] "ON"
class(entry["Ontario"])
# [1] "list"
# Returns single element/value
j <- entry[["Ontario"]]
class(j)
# [1] "character"
as.numeric(entry[j])
# [1] 13.6
j <- coupled wiith [[ forces a walk to the end of the chain that is some value, here '13.6'. Concerning quoting: A little less mysterious under lengths(entry) Ontario ON 1 1 so entry$ON [1] "13.6". entry2 <- list(Ontario = 'ON', ON = '13.6') also works because as read from left to right by compiler, ON (without quotes in second position) is an object, created in first position 'ON', so entry2$ON [1] "13.6", while entry3 <- list(Ontario = ON, ON = '13.6')` Error: object 'ON' not found, because not created yet.
[with[[: stackoverflow.com/q/1169456/3358272, stackoverflow.com/q/45918827/3358272; stackoverflow.com/q/18222286/3358272