CODEWITHSUNDEEP
r
Herminio Sabino
Herminio Sabino

Reputation: 19

count and add precipitation values of 5 consecutive days or more below 2 mm in R

I have a rainfall time series and would like to know the accumulated amount of rainfall that spanned 5 days or more.

My data are daily observations as shown below.

Date Prec
1983-01-01 1.12
1983-01-02 1.08
1983-01-03 1.11
1983-01-04 2.00
1983-01-05 1.44
1983-01-06 3.12
1983-01-07 0.12
1983-01-08 0.52
1983-01-09 1.62
1983-01-10 0.12
1983-01-11 1.33
1983-01-12 1.14
1983-01-13 1.16
1983-01-14 1.00
1983-01-15 5.12
1983-01-16 6.12

I've already got the sum of days by setting a range of days (5 consecutive days), but there is the possibility of having a longer sequence of days that meet my condition.

prec <- transform(prec, extreme =+(Prec < 2))
r <- rle(prec$extreme)
r$values[r$values == 1] <- r$lengths[r$values == 1]
prec <- transform(prec, n=unlist(Map(rep, r$values, 
r$lengths)))

and the result I hope is this: enter image description here

I've already got the sum of days by setting a range of days (5 consecutive days), but there is the possibility of having a longer sequence of days that meet my condition. And I want there to be columns of total consecutive days (Prec < 2), cumulative total of those consecutive days, start date and end date of the sequence.

Thanks in advance!

Upvotes: 0

Views: 346

Answers (1)

Martin Gal
Martin Gal

Reputation: 16978

You could use dplyr:

library(dplyr)

 data %>% 
  group_by(grp = cumsum(Prec > 2)) %>%
  filter(Prec <= 2) %>%  
  summarise(start_date = min(Date),
            end_date = max(Date),
            rain_acc = sum(Prec), 
            days_con = n()) %>% 
  select(-grp)

returns

# A tibble: 2 x 4
  start_date end_date   rain_acc days_con
  <date>     <date>        <dbl>    <int>
1 1983-01-01 1983-01-05     6.75        5
2 1983-01-07 1983-01-14     7.01        8

Data

structure(list(Date = structure(c(4748, 4749, 4750, 4751, 4752, 
4753, 4754, 4755, 4756, 4757, 4758, 4759, 4760, 4761, 4762, 4763
), class = "Date"), Prec = c(1.12, 1.08, 1.11, 2, 1.44, 3.12, 
0.12, 0.52, 1.62, 0.12, 1.33, 1.14, 1.16, 1, 5.12, 6.12)), class = c("spec_tbl_df", 
"tbl_df", "tbl", "data.frame"), row.names = c(NA, -16L), spec = structure(list(
    cols = list(Date = structure(list(format = ""), class = c("collector_date", 
    "collector")), Prec = structure(list(), class = c("collector_double", 
    "collector"))), default = structure(list(), class = c("collector_guess", 
    "collector")), skip = 1L), class = "col_spec"))

Upvotes: 1

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