There is no `value` column in the `dput` output shown in the
question so using `tmin` instead note that the `width=` argument
of `rollapply` can be a list containing a vector of offsets (-1 is prior
value, -2 is value before that, etc.) and that we can use `rollapplyr`
with an `r` on the end to get right alignment. See `?rollapply`
library(dplyr)
library(zoo)
roll <- function(x, k) rollapplyr(x, list(-seq(1:k)), mean, fill = NA)
df %>%
group_by(citycode) %>%
mutate(mean2 = roll(tmin, 2), mean3 = roll(tmin, 3), mean4 =
roll(tmin, 4)) %>%
ungroup
(The code above has been indented 2 spaces so you can
identify inadvertent line wrapping by the email system.)
On Sun, Mar 25, 2018 at 10:48 AM, Miluji Sb <miluj...@gmail.com> wrote:
> Dear all,
>
> I have weekly data by city (variable citycode). I would like to take the
> average of the previous two, three, four weeks (without the current week)
> of the variable called value.
>
> This is what I have tried to compute the average of the two previous weeks;
>
> df = df %>%
> mutate(value.lag1 = lag(value, n = 1)) %>%
> mutate(value .2.previous = rollapply(data = value.lag1,
> width = 2,
> FUN = mean,
> align = "right",
> fill = NA,
> na.rm = T))
>
> I crated the lag of the variable first and then attempted to compute the
> average but this does not seem to to what I want. What I am doing wrong?
> Any help will be appreciated. The data is below. Thank you.
>
> Sincerely,
>
> Milu
>
> dput(droplevels(head(df, 10)))
> structure(list(year = c(1970L, 1970L, 1970L, 1970L, 1970L, 1970L,
> 1970L, 1970L, 1970L, 1970L), citycode = c(1L, 1L, 1L, 1L, 1L,
> 1L, 1L, 1L, 1L, 1L), month = c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L,
> 2L, 3L), week = c(1L, 2L, 3L, 4L, 5L, 5L, 6L, 7L, 8L, 9L), date =
> structure(c(1L,
> 2L, 3L, 4L, 5L, 5L, 6L, 7L, 8L, 9L), .Label = c("1970-01-10",
> "1970-01-17", "1970-01-24", "1970-01-31", "1970-02-07", "1970-02-14",
> "1970-02-21", "1970-02-28", "1970-03-07"), class = "factor"),
> value = c(-15.035, -20.478, -22.245, -23.576, -8.84099999999995,
> -18.497, -13.892, -18.974, -15.919, -13.576)), .Names = c("year",
> "citycode", "month", "week", "date", "tmin"), row.names = c(NA,
> 10L), class = "data.frame")
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
