[R] HELP boxplot for time class

[uvilla]

hi again

I will try this time to explain my problem clearly
I have the following data from the file skiing.csv (3 first rows)

 protokollid     date        start      end
1            4 2/23/2009  8:50:10 15:17:30
2            4 2/24/2009  9:47:00 13:52:25
3            5 3/22/2009  8:51:25 12:00:05


I have the following script

library(chron) 

skiers=read.csv("skiing.csv")
strptime("08:50:10","%H:%M:%S") 

start=times(skiers[,3])
strptime(start,"%H:%M:%S")  
end=times(skiers[,4])
strptime(end,"%H:%M:%S") 

#calc lenght of the route
length.route=end-start

#calc medians
median(start)
median(length.route) 

Then I want to do a box plot of the staring time
when I use:

boxplot(start)   

this error appears: Warning message:
In is.na(x) : is.na() applied to non-(list or vector) of type 'NULL'

when I try to convert start as POSIXct

> start=as.POSIXct(start)
Error in as.POSIXct.default(start) : 
  do not know how to convert 'start' to class "POSIXlt"

and when I try to convert skiers[,3] as POSIXct

> skiers[,3]=as.POSIXct(skiers[,3])
Error in as.POSIXlt.character(as.character(x)) : 
  character string is not in a standard unambiguous format

start is of "times" class and skiers[,3] of "factor" class

I want to do a boxplot of the starting time of my data, which reflect the
median " 08:36:45", and all O get in the y axis are decimal numbers :(
Help please

Best regards

Maria Stauss


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