R help - Jun 2011 - median time period

Hello List

I'm trying to calculate the median period (in months) of a set of time
intervals (between two interventions).

I have been playing with the lubridate package to create the intervals but I
can't think of the right approach to get the median timeperiod.

Toy code:

library(lubridate)
test <- c('08-04-22', '08-07-28', '09-03-02',
'09-03-03', '09-01-30', '09-03-09', '10-02-24',
'10-03-05')
test <- ymd(test)
intervals <- as.period(test[5:8] - test[1:4])

intervals
[1] 9 months and 8 days    7 months and 9 days    11 months and 22 days 
[4] 1 year and 2 days 

How can I convert this 'period' object to months? From there I think I
should just convert to 'numeric' and calculate the median.

Garrett if you're out there - great package but could you help please!?

Best

iain
> sessionInfo()
R version 2.13.0 (2011-04-13)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_GB.utf8       LC_NUMERIC=C             
 [3] LC_TIME=en_GB.utf8        LC_COLLATE=en_GB.utf8    
 [5] LC_MONETARY=C             LC_MESSAGES=en_GB.utf8   
 [7] LC_PAPER=en_GB.utf8       LC_NAME=C                
 [9] LC_ADDRESS=C              LC_TELEPHONE=C           
[11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C      

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] lubridate_0.2.4

loaded via a namespace (and not attached):
[1] plyr_1.5.2  stringr_0.4

Typical - you post to the list and then work it out for yourself!

Anyway here's my solution

Toy code as before then:

intervalsMonths <- 12 * intervals$year + intervals$month

#convert whole years to months then add the remaining months for that entry in
intervals

medianMonths <- median(as.numeric(intervalsMonths))

Best

iain

--- On Wed, 29/6/11, Iain Gallagher <iaingallagher at btopenworld.com>
wrote:
> From: Iain Gallagher <iaingallagher at btopenworld.com>
> Subject: [R] median time period
> To: r-help at r-project.org
> Date: Wednesday, 29 June, 2011, 16:24
> Hello List
> 
> I'm trying to calculate the median period (in months) of a
> set of time intervals (between two interventions). 
> 
> I have been playing with the lubridate package to create
> the intervals but I can't think of the right approach to get
> the median timeperiod.
> 
> Toy code:
> 
> library(lubridate)
> test <- c('08-04-22', '08-07-28', '09-03-02',
> '09-03-03', '09-01-30', '09-03-09',
'10-02-24', '10-03-05')
> test <- ymd(test)
> intervals <- as.period(test[5:8] - test[1:4])
> 
> intervals
> [1] 9 months and 8 days? ? 7 months and 9
> days? ? 11 months and 22 days 
> [4] 1 year and 2 days 
> 
> How can I convert this 'period' object to months? From
> there I think I should just convert to 'numeric' and
> calculate the median.
> 
> Garrett if you're out there - great package but could you
> help please!?
> 
> Best
> 
> iain
> 
> > sessionInfo()
> R version 2.13.0 (2011-04-13)
> Platform: x86_64-pc-linux-gnu (64-bit)
> 
> locale:
>  [1] LC_CTYPE=en_GB.utf8? ?
> ???LC_NUMERIC=C? ? ? ?
> ? ???
>  [3] LC_TIME=en_GB.utf8? ? ? ?
> LC_COLLATE=en_GB.utf8? ? 
>  [5] LC_MONETARY=C? ? ? ? ?
> ???LC_MESSAGES=en_GB.utf8???
>  [7] LC_PAPER=en_GB.utf8? ?
> ???LC_NAME=C? ? ? ?
> ? ? ? ? 
>  [9] LC_ADDRESS=C? ? ? ? ? ?
> ? LC_TELEPHONE=C? ? ? ?
> ???
> [11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C?
> ? ? 
> 
> attached base packages:
> [1] stats? ???graphics? grDevices
> utils? ???datasets?
> methods???base? ???
> 
> other attached packages:
> [1] lubridate_0.2.4
> 
> loaded via a namespace (and not attached):
> [1] plyr_1.5.2? stringr_0.4
> 
> 
> ______________________________________________
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