R help - Aug 2011 - Finding an average time spent

Hello R help! 

I am extremely new to R (as in 3 just days) and I've been using it to do
some pretty basic things. I am frustratingly stuck on one point, and am so
so so close to figuring it out, but just far enough away to ask for some
(perhaps embarrassingly easy) help.

I have a dataset, visitors, that has a variable called Time.Spent.
Time.Spent consists of times in the format hh:mm:ss , and it is a
measurement, kind of like a timer, of the amount of time someone spent in a
museum exhibit. 

I need to find the average time spent.  I've figured the easiest way to do
this would be to convert it into seconds. I found a function that someone
wrote on how to do this here:
http://stackoverflow.com/questions/1389428/dealing-with-time-periods-such-as-5-minutes-and-30-seconds-in-r

I thought this would be the answer! However, when I run the code, it works
perfectly for the first variable in the first observation, but then repeats
the same answer all the way down the rows. 

Sorry for the wordiness, here's the code I have:

# The function to convert hh:mm:ss into just seconds:

time.to.seconds <- function(time) {
   time <- strsplit(time, ":")[[1]]
   return ((as.numeric(time[1]) * 60 * 60) + (as.numeric(time[2]) * 60) +
(as.numeric(time[3])))
}

# I've tried many things to then create a new variable in the dataset
visitors:

visitors$TimeInSeconds <- time.to.seconds(time=c(visitors$Time.Spent))

# Or

visitors$TimeInSeconds <- time.to.seconds(visitors$Time.Spent)


I figure it has something to do with the fact that strsplit() makes a list?
Do I need a loop to go through each variable? I know this is a huge question
but any hints at al would be very much appreciated. 


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On Fri, Aug 12, 2011 at 4:23 PM, erinbspace <erin.braswell at gmail.com>
wrote:
> Hello R help!
>
> I am extremely new to R (as in 3 just days) and I've been using it to
do
> some pretty basic things. I am frustratingly stuck on one point, and am so
> so so close to figuring it out, but just far enough away to ask for some
> (perhaps embarrassingly easy) help.
>
> I have a dataset, visitors, that has a variable called Time.Spent.
> Time.Spent consists of times in the format hh:mm:ss , and it is a
> measurement, kind of like a timer, of the amount of time someone spent in a
> museum exhibit.
>
> I need to find the average time spent. ?I've figured the easiest way to
do
> library(chron)
> Time.Spent <- c("12:12:10", "13:12:10")
> times(mean(as.numeric(times(Time.Spent))))
[1] 12:42:10

-- 
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com

On 08/13/2011 06:23 AM, erinbspace wrote:
> Hello R help!
>
> I am extremely new to R (as in 3 just days) and I've been using it to
do
> some pretty basic things. I am frustratingly stuck on one point, and am so
> so so close to figuring it out, but just far enough away to ask for some
> (perhaps embarrassingly easy) help.
>
> I have a dataset, visitors, that has a variable called Time.Spent.
> Time.Spent consists of times in the format hh:mm:ss , and it is a
> measurement, kind of like a timer, of the amount of time someone spent in a
> museum exhibit.
>
> I need to find the average time spent.  I've figured the easiest way to
do
> this would be to convert it into seconds. I found a function that someone
> wrote on how to do this here:
>
http://stackoverflow.com/questions/1389428/dealing-with-time-periods-such-as-5-minutes-and-30-seconds-in-r
>
> I thought this would be the answer! However, when I run the code, it works
> perfectly for the first variable in the first observation, but then repeats
> the same answer all the way down the rows.
>
> Sorry for the wordiness, here's the code I have:
>
> # The function to convert hh:mm:ss into just seconds:
>
> time.to.seconds<- function(time) {
>     time<- strsplit(time, ":")[[1]]
>     return ((as.numeric(time[1]) * 60 * 60) + (as.numeric(time[2]) * 60) +
> (as.numeric(time[3])))
> }
>
> # I've tried many things to then create a new variable in the dataset
> visitors:
>
> visitors$TimeInSeconds<- time.to.seconds(time=c(visitors$Time.Spent))
>
> # Or
>
> visitors$TimeInSeconds<- time.to.seconds(visitors$Time.Spent)
>
>
> I figure it has something to do with the fact that strsplit() makes a list?
> Do I need a loop to go through each variable? I know this is a huge
question
> but any hints at al would be very much appreciated.
>
Hi erinbspace,
By hard coding the [[1]] in your function, you are automatically taking 
the first element of any list. If you want to convert a vector of times, 
try this:

time.to.seconds<- function(time) {
  time<-strsplit(time, ":")[[1]]
  return(as.numeric(time[1]) * 3600 + as.numeric(time[2]) * 60 +
   as.numeric(time[3]))
}
watch.times<-c("0:2:31","0:4:12","0:0:47")
# use sapply to step through the vector of times
sapply(watch.times,time.to.seconds)
0:2:31 0:4:12 0:0:47
    151    252     47

Jim