Hello,
There are obvious bugs in your code, you are testing for light > 2 or
ligth < 2 but this would mean that dusk and dawn are undetermined for
light == 2 and that they happen at light == 1.
Without loops or compound logical conditions:
f <- function(x){
x$dawn <- x$time[ which.min(x$light) ]
x$dusk <- x$time[ max(which(x$light == 0)) + 1 ]
x
}
do.call(rbind, by(d, d$day, f))
Hope this helps,
Rui Barradas
Em 15-07-2012 17:32, Santiago Guallar escreveu:
Hi,
I have a dataset which contains several time records for a number of days, plus a
variable (light) that allows to determine night time (lihgt= 0) and daytime
(light> 0). I need to obtain get dusk time and dawn time for each day and place
them in two columns.
This is the starting point (d):
day time light
1 1 20
1 12 10
1 11 6
1 9 0
1 6 0
1 12 0
...
30 8 0
30 3 0
30 8 0
30 3 0
30 8 8
30 9 20
And this what I want to get:
day time light dusk dawn
1 1 20 11 10
1 12 10 11 10
1 11 6 11 10
1 9 0 11 10
1 6 0 11 10
1 12 0 11 10
...
30 8 0 9 5
30 3 0 9 5
30 8 0 9 5
30 3 0 9 5
30 8 8 9 5
30 9 20 9 5
This is the code for data frame d:
day= rep(1:30, each=10)
n= length(dia); x= c(1:24)
time= sample(x, 300, replace= T)
light= rep(c(20,10,6,0,0,0,0,0,8,20), 30)
d=data.frame(day,time,light)
I'd need to impose a double condition like the next but if does not take more
than one:
attach(d)
for (i in 1: n){
if (light[i-1]>2 & light[i]<2){
d$dusk<- time[i-1]
}
if (light[i-1]<2 & light[i]>2){
d$dawn<- time[i]
}
}
detach(d)
d
Thank you for your help
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