[R] R - Aggregate 3-Hourly Block Data into Weekly (Melt)

[Shouro Dasgupta]

I am trying to compute max, min, and mean from Global Circulation Models
(GCM) for the US. The data is in 3-hour blocks for 2026-2045 and 2081-2100.
Sample Data:

tmp1 <- structure(list(FIPS = c(1001L, 1003L, 1005L), X2026.01.01.1 =
c(285.5533142,
  285.5533142, 286.2481079), X2026.01.01.2 = c(283.4977112, 283.4977112,
  285.0860291), X2026.01.01.3 = c(281.9733887, 281.9733887, 284.1548767
  ), X2026.01.01.4 = c(280.0234985, 280.0234985, 282.6075745),
      X2026.01.01.5 = c(278.7125854, 278.7125854, 281.2553711),
      X2026.01.01.6 = c(278.5204773, 278.5204773, 280.6148071)),
.Names = c("FIPS",
  "X2026.01.01.1", "X2026.01.01.2", "X2026.01.01.3", "X2026.01.01.4",
  "X2026.01.01.5", "X2026.01.01.6"), class = "data.frame", row.names = c(NA,
  -3L))

I have extracted the data by FIPS code and reshaped the yearly data files
using melt();

for (i in filelist) {
  tmp1 <- as.data.table(read.csv(i,header=T, sep=","))
  tmp2 <- melt(tmp1, id="FIPS")
  tmp2$year <- as.numeric(substr(tmp2$variable,2,5))
  tmp2$month <- as.numeric(substr(tmp2$variable,7,8))
  tmp2$day <- as.numeric(substr(tmp2$variable,10,11))}

I have added datestring and weekdays using the following code:
Inserting Date Variable

tmp2$date <- with(tmp2, ymd(sprintf('%04d%02d%02d', year, month, day)))

Inserting Day Variable

tmp2$day <- weekdays(as.Date(tmp2$date))

sample.tmp2 <- "FIPS         xdate     temp year month      day
date      dates weekdays
+ 5599311  1003 X2045.08.14.2 304.5995 2045     8   Monday 2045-08-14
2036-01-29        2
+ 468406  39093 X2045.01.19.7 267.8483 2045     1 Thursday 2045-01-19
2028-06-04        0
+ 5022078 21167 X2045.07.21.8 314.6772 2045     7   Friday 2045-07-21
2035-09-13        4
+ 186822   9005 X2045.01.08.5 269.0803 2045     1   Sunday 2045-01-08
2037-06-28        0
+ 3998678 13295 X2045.06.10.7 307.2408 2045     6 Saturday 2045-06-10
2033-10-13        4"

Data <- read.table(text=sample.tmp2, header = TRUE)

My goal is to aggregate these 3-hourly blocks into weekly data, however,
GCM data is not consistent and the blocks vary between 7 and 8. I want to
clip the data to start on the first Monday of 2026 and end on the last
Sunday of 2045 and then use rep() to assign week numbers for the whole
epoch.

I know I can count the number of each day using something like this;

length(which(weekdays == '0'))

Where 0, 1, 2..., 6 represent Sunday, Monday,...

My question is am I doing anything wrong in trying to aggregate the data to
begin with? But importantly, I would be grateful for any help to clip the
dataset to begin on the first Monday and end on the last Sunday. Thank you
very much!

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