how to create a function or loop that can sum a certain amount of rows above it from another column-CodePudding

I am trying to calculate degree heating weeks in the Ocean and was wondering how I could create a loop or some other methods that would calculate this value and put it in a new column(DHW) for each row. DHW is a value calculated for each day.

It is calculated over a 12-week rolling window (84 days) from another column of values (hotspot). DHW is the sum of those 84 rows (value in its own row(day) plus the 83 above it) and then divided by 7

Below is an example of my data frame, I am just using the Hotspot column to calculate DHW

CodePudding user response：

if I understood correctly

fix width = 3 to width = 84

df <-
  data.frame(DAYS = seq(as.Date("2022-01-01"), length.out = 10,  by = "1 days"),
             HS = seq(10))

library(dplyr)

df %>%
  mutate(DWH = zoo::rollapply(
    HS,
    width = 3,
    FUN = function(x) sum(x) / 7,
    fill = NA,
    align = "right"
  ))
#>          DAYS HS       DWH
#> 1  2022-01-01  1        NA
#> 2  2022-01-02  2        NA
#> 3  2022-01-03  3 0.8571429
#> 4  2022-01-04  4 1.2857143
#> 5  2022-01-05  5 1.7142857
#> 6  2022-01-06  6 2.1428571
#> 7  2022-01-07  7 2.5714286
#> 8  2022-01-08  8 3.0000000
#> 9  2022-01-09  9 3.4285714
#> 10 2022-01-10 10 3.8571429

^{Created on 2022-07-04 by the reprex package (v2.0.1)}