Arrange function in plyr - r

Question

As I was doing the final assignment of coursera R programming course, my arrange function didnt actually worked well and I am fairly confused
as I have extract the state by split function
my_data<- outcome[,c(2,7,23)]
names(my_data)<- c("hospital","state","heart_attack","heart_failure","pneumonia")
my_data1<-lapply(split(my_data,my_data$state), data.frame)
my_data2<-arrange(my_data1$stateName, penumonia)
> arrange(my_data1$AK, pneumonia)
hospital state pneumonia
1 PROVIDENCE ALASKA MEDICAL CENTER AK 10.5
2 PEACEHEALTH KETCHIKAN MEDICAL CENTER AK 11.3
3 SITKA COMMUNITY HOSPITAL AK 11.5
4 BARTLETT REGIONAL HOSPITAL AK 11.6
5 NORTON SOUND REGIONAL HOSPITAL AK 11.6
6 PROVIDENCE KODIAK ISLAND MEDICAL CTR AK 12.0
7 MAT-SU REGIONAL MEDICAL CENTER AK 12.1
8 SOUTH PENINSULA HOSPITAL AK 12.2
9 ALASKA REGIONAL HOSPITAL AK 12.5
10 FAIRBANKS MEMORIAL HOSPITAL AK 13.4
11 CENTRAL PENINSULA GENERAL HOSPITAL AK 13.8
12 MT EDGECUMBE HOSPITAL AK 14.2
13 ALASKA NATIVE MEDICAL CENTER AK 15.5
14 YUKON KUSKOKWIM DELTA REG HOSPITAL AK 9.7
which obviously
14 YUKON KUSKOKWIM DELTA REG HOSPITAL AK 9.7
should be at the top.
Same result after I transform the column class to numeric.
So I have transformed the pneumonia column with
> class(my_data2$pneumonia)
[1] "character"
> my_data2$pneumonia <-as.numeric(my_data2$pneumonia)
Warning message:
NAs introduced by coercion
> class(my_data2$pneumonia)
[1] "numeric
> arrange(my_data2,pneumonia)
hospital state pneumonia
1 YUKON KUSKOKWIM DELTA REG HOSPITAL AK 9.7
2 PROVIDENCE ALASKA MEDICAL CENTER AK 10.5
3 PEACEHEALTH KETCHIKAN MEDICAL CENTER AK 11.3
4 SITKA COMMUNITY HOSPITAL AK 11.5
5 BARTLETT REGIONAL HOSPITAL AK 11.6
6 NORTON SOUND REGIONAL HOSPITAL AK 11.6
7 PROVIDENCE KODIAK ISLAND MEDICAL CTR AK 12.0
8 MAT-SU REGIONAL MEDICAL CENTER AK 12.1
9 SOUTH PENINSULA HOSPITAL AK 12.2
10 ALASKA REGIONAL HOSPITAL AK 12.5
11 FAIRBANKS MEMORIAL HOSPITAL AK 13.4
12 CENTRAL PENINSULA GENERAL HOSPITAL AK 13.8
13 MT EDGECUMBE HOSPITAL AK 14.2
14 ALASKA NATIVE MEDICAL CENTER AK 15.5
15 PROVIDENCE VALDEZ MEDICAL CENTER AK NA
16 PROVIDENCE SEWARD HOSPITAL AK NA
17 CORDOVA COMMUNITY MEDICAL CENTER AK NA
and the problem solved, thanks for comment