R help - Jun 2013 - modify and append new rows to a data.frame using ddply

Hi,

I have a data.frame that contains a variable act which records the duration (in
seconds) of two states (wet-dry) for several individuals (identified by Ring)
over a period of time. Since I want to work with daytime (i.e. from sunrise till
sunset) and night time (i.e. from sunset till next sunrise), I have to split act
from time[i] till sunset and from sunset until time[i+1], and from time[k] till
sunrise and from sunrise until time[k+1].

Here is an example with time and act separated by a comma:

[i] 01-01-2000 20:55:00 , 360?
[i+1] 01-01-2000 21:01:00 , 30 # let's say that sunset is at 01-01-2000
21:00:00

[i+2]?01-01-2000 21:01:30 , 30

.
.
.
My goal is to get:
[i]?01-01-2000 20:55:00 , 300 # act is modified

[i+1]?01-01-2000 21:00:00 , 60 # new row with time=sunset

[i+2]?01-01-2000 21:01:00 , 30 # previously row i+1th

[i+3]?01-01-2000 21:01:30 , 30 # previously row i+2th

.
.
.
I attach a dput with a selection of my data.frame. Here is a piece of existing
code that I am trying to adapt just for the daytime/night time change:

? require(plyr)

? xandaynight <- ddply( xan, .(Ring), function(df1){
? # index of day/night changes
? ind <- c( FALSE, diff(df$dif) == 1 )
? add <- df1[ind,]
? add$timepos <- add$dusk
? # rearrangement
? df1 <- rbind( df1, add )
? df1 <- df1[order(df1$timepos),]
? # recalculation of act
? df1$act2 <- c( diff( as.numeric(df1$timepos) ), NA )
? df1} )

This code produces an error message:
"Error en diff(df$dif): error in evaluating the argument 'x' in
selecting a method for function 'diff': Error en df$dif: object of type
'closure' is not a subset"

Thank you for your help,

Santi

On 10-06-2013, at 11:49, Santiago Guallar <sguallar at yahoo.com> wrote:
> Hi,
> 
> I have a data.frame that contains a variable act which records the duration
(in seconds) of two states (wet-dry) for several individuals (identified by
Ring) over a period of time. Since I want to work with daytime (i.e. from
sunrise till sunset) and night time (i.e. from sunset till next sunrise), I have
to split act from time[i] till sunset and from sunset until time[i+1], and from
time[k] till sunrise and from sunrise until time[k+1].
> 
> Here is an example with time and act separated by a comma:
> 
> [i] 01-01-2000 20:55:00 , 360 
> [i+1] 01-01-2000 21:01:00 , 30 # let's say that sunset is at 01-01-2000
21:00:00
> 
> [i+2] 01-01-2000 21:01:30 , 30
> 
> .
> .
> .
> My goal is to get:
> [i] 01-01-2000 20:55:00 , 300 # act is modified
> 
> [i+1] 01-01-2000 21:00:00 , 60 # new row with time=sunset
> 
> [i+2] 01-01-2000 21:01:00 , 30 # previously row i+1th
> 
> [i+3] 01-01-2000 21:01:30 , 30 # previously row i+2th
> 
> .
> .
> .
> I attach a dput with a selection of my data.frame. Here is a piece of
existing code that I am trying to adapt just for the daytime/night time change:
> 
>   require(plyr)
> 
>   xandaynight <- ddply( xan, .(Ring), function(df1){
>   # index of day/night changes
>   ind <- c( FALSE, diff(df$dif) == 1 )
>   add <- df1[ind,]
>   add$timepos <- add$dusk
>   # rearrangement
>   df1 <- rbind( df1, add )
>   df1 <- df1[order(df1$timepos),]
>   # recalculation of act
>   df1$act2 <- c( diff( as.numeric(df1$timepos) ), NA )
>   df1} )
> 
> This code produces an error message:
> "Error en diff(df$dif): error in evaluating the argument 'x'
in selecting a method for function 'diff': Error en df$dif: object of
type 'closure' is not a subset"
> 
Shouldn't the line

  ind <- c( FALSE, diff(df$dif) == 1 )

read

  ind <- c( FALSE, diff(df1$dif) == 1 )

Berend