r - Find value in previous and next year -


i have dataframe timeseries observations. each observation add variable value @ closest similar date in previous year , closest similar date in next year (e.g. value of 15 may 2014, might 13 may 2013 , 21 may 2015). there smart way, e.g. using dplyr, this? please find example code below (most code focused on creating random set of dates , value, earlier question). many in advance.

       date    value nearest_val_nextyear nearest_val_prevyear 1  2009-02-14 6.511781                    0                    0 2  2009-12-23 5.389843                    0                    0 3  2011-08-01 4.378759                    0                    0 4  2014-04-07 2.785300                    0                    0 5  2008-08-12 6.124931                    0                    0 6  2014-03-10 4.955066                    0                    0 7  2014-07-23 4.983810                    0                    0 8  2012-04-14 5.943836                    0                    0 9  2012-01-13 5.821221                    0                    0 10 2007-06-30 5.593901                    0                    0 11 2008-08-24 5.918977                    0                    0 12 2008-05-30 5.782136                    0                    0 13 2012-06-30 5.074565                    0                    0 14 2010-01-27 3.010648                    0                    0 15 2013-02-27 5.619826                    0                    0 16 2010-12-25 4.943871                    0                    0 17 2012-09-27 4.844204                    0                    0 18 2014-12-08 3.529248                    0                    0 19 2010-01-15 4.521850                    0                    0 20 2013-03-21 5.417942                    0                    0    # set start , end dates sample between day.start <- "2007/01/01" day.end <- "2014/12/31"  set.seed(1) # define random date/time selection function rand.day.time <- function(day.start,day.end,size) {   dayseq <- seq.date(as.date(day.start),as.date(day.end),by="day")   dayselect <- sample(dayseq,size,replace=true)   as.posixlt(paste(dayselect) ) }  dateval=rand.day.time(day.start,day.end,size=20) value=rnorm(n=20,mean=5,sd=1) df=data.frame(date=dateval,value=value) df$nearest_val_nextyear=0 df$nearest_val_prevyear=0 df

this not smart way of doing this, i'm posting hopes someone, maybe you, can make smart/pretty.

library(dplyr) library(lubridate) dat <- data.frame(dateval, value) dat <- dat %>% mutate(year = year(dateval), nv_next = na, nv_prev = na) #you don't need dplyr this...  shifts <- c(1, -1) #nextyear, prevyear  (s in 1:2) { #once each shift   (i in 1:nrow(dat)) {     otheryear <- dat[dat[,"year"]==dat[i,"year"]+shifts[s],] #subset df dates of other year     if (nrow(otheryear) == 0) { #ends if there's no other year       dat[i,3+s] <- na     } else {       cands <- otheryear$dateval #candidates have value chosen       cands_shifted <- cands       year(cands_shifted) <- dat[i,"year"] #change year in cand's copy       nearest_date <- which.min(abs(difftime(dat[i,"dateval"], cands_shifted))) #after years same, closest date can calculated difftime       dat[i,3+s] <- dat[dat$dateval == cands[nearest_date],"value"] #we check on cands real date was, , assign it's value     }      } }

this resulted in

> dat       dateval    value year  nv_next  nv_prev 1  2009-02-14 6.511781 2009 3.010648 5.782136 2  2009-12-23 5.389843 2009 4.943871 5.918977 3  2011-08-01 4.378759 2011 5.074565 4.943871 4  2014-04-07 2.785300 2014       na 5.417942 5  2008-08-12 6.124931 2008 5.389843 5.593901 6  2014-03-10 4.955066 2014       na 5.619826 7  2014-07-23 4.983810 2014       na 5.417942 8  2012-04-14 5.943836 2012 5.417942 4.378759 9  2012-01-13 5.821221 2012 5.619826 4.378759 10 2007-06-30 5.593901 2007 5.782136       na 11 2008-08-24 5.918977 2008 5.389843 5.593901 12 2008-05-30 5.782136 2008 6.511781 5.593901 13 2012-06-30 5.074565 2012 5.417942 4.378759 14 2010-01-27 3.010648 2010 4.378759 6.511781 15 2013-02-27 5.619826 2013 4.955066 5.821221 16 2010-12-25 4.943871 2010 4.378759 5.389843 17 2012-09-27 4.844204 2012 5.417942 4.378759 18 2014-12-08 3.529248 2014       na 5.417942 19 2010-01-15 4.521850 2010 4.378759 6.511781 20 2013-03-21 5.417942 2013 4.955066 5.943836

i nested loops instead of using copy each shift, must careful nv_next , nv_prev since selected index , not name.


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