[R] Help with loop

[Rui Barradas]

Hello,

If I understand it well, this might avoid a loop.

dat <- read.table(text="
  Salt       time
1  35.65114 2003-07-19
2  35.64226 2003-07-20
3  35.62411 2003-07-21
4  35.62473 2003-07-22
5  35.65893 2003-07-23
6  35.70140 2003-07-24
7  35.62157 2003-07-25
8  35.64122 2003-07-26
9  35.63515 2003-07-27
10 35.63798 2003-07-28
", header = TRUE, stringsAsFactors = FALSE)

dat$time <- as.Date(dat$time)

change <- cumsum(c(FALSE, abs(diff(dat$Salt)) > 0.05))
split(dat, change)


Hope this helps,

Rui Barradas
Em 21-11-2012 16:39, Hefri escreveu:
> Hi,
>
> I have used R for some time, but managed to avoid writing  loops. But this
> time I am afraid there is no way around it.
>
> I have a dataframe with time and salinity (see below). I would like to
> extract the time intervals where salinity changes by less than 0.05. So
> using the values below this would mean that a subset was made from
> 2003-07-19 to 2003-07-24, where the change in salinity exceeded 0.05, and
> then stating again from 2003-07-24. In other words, I want to make subset of
> the time intervals where the one variable stays stabile within a certain set
> range.
>
>> head (D, 10)
>         Salt       time
> 1  35.65114 2003-07-19
> 2  35.64226 2003-07-20
> 3  35.62411 2003-07-21
> 4  35.62473 2003-07-22
> 5  35.65893 2003-07-23
> 6  35.70140 2003-07-24
> 7  35.62157 2003-07-25
> 8  35.64122 2003-07-26
> 9  35.63515 2003-07-27
> 10 35.63798 2003-07-28
>
> Is this possible? Can some please help with how I need to write the loop to
> achieve this?
>
> Many thanks, Helen
>
>
>
>
> --
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