Subset by function's variable using $variable

Question

I am having trouble to subset from a list using a variable of my function.

rankhospital <- function(state,outcome,num = "best") {

#code here

e3<-dataframe(...,state.name,...)


if (num=="worst"){ return(worst(state,outcome))
}else if((num%in%b=="TRUE" & outcome=="heart attack")=="TRUE"){
 sep<-split(e3,e3$state.name)
 hosp.estado<-sep$state
 hospital<-hosp.estado[num,1]
 return(as.character(hospital))

I split my data frame by state (which is a variable of my function) But hosp.estado<-sep$state doesn't work. I have also tried as.data.frame.

The function (rankhospital("NY"....) returns me a character(0).

When I feed the sep$state with sep$"NY" directly in code it works perfectly so I guess the problem is I can't use a function's variable to do this. Am I right? What could I use instead?

Thank you!!

Also, your if-condition is needlessly complicated. num %in% b & outcome=="heart attack" would do just as well. — RoyalTS
– RoyalTS, Commented Jan 24, 2014 at 23:20

jlhoward · Accepted Answer · 2014-01-24 23:29:12Z

1

If state is a variable in your function, you can refer to a column with the name given by state using: sep[state] or sep[[state]]. The first produces a data frame with one column named based on the value of state. The second produces an unnamed vector.

df=data.frame(NY=rnorm(10),CA=rnorm(10), IL=rnorm(10))
state="NY"
df[state]
#             NY
# 1  -0.79533912
# 2  -0.05487747
# 3   0.25014132
# 4   0.61824329
# 5  -0.17262350
# 6  -2.22390027
# 7  -1.26361438
# 8   0.35872890
# 9  -0.01104548
# 10 -0.94064916
df[[state]]
#  [1] -0.79533912 -0.05487747  0.25014132  0.61824329 -0.17262350 -2.22390027 -1.26361438  0.35872890 -0.01104548 -0.94064916

class(df[state])
# [1] "data.frame"

class(df[[state]])
# [1] "numeric"

edited Jan 24, 2014 at 23:29

answered Jan 24, 2014 at 23:23

jlhoward

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BrodieG · Accepted Answer · 2014-01-24 23:20:12Z

0

It seems like you are trying to get the top hospital in a state. You don't want to split here (see the result of sep to see what I mean). Instead, use:

as.character(e3[e3$state.name==state, 1][num])

This hopefully does what you want.

answered Jan 24, 2014 at 23:20

BrodieG

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lukeA · Accepted Answer · 2014-01-25 02:29:48Z

0

You need sep[[state]] instead of sep$state to get the data frame out of your sep list, which matches the state parameter of your function. Like this:

e3 <- read.csv("https://raw.github.com/Hindol/data-analysis-coursera/master/HW3/hospital-data.csv")

state <- "WY"
num <- 1:5

sep<-split(e3,e3$State)
hosp.estado<-sep[[state]]
hospital<-hosp.estado[num,1]
as.character(hospital)
# [1] "530002" "530006" "530008" "530010" "530011"

answered Jan 25, 2014 at 2:29

lukeA

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