Calculate the number of days, weekdays or weeks in a month, quarter, half-year or year.

weekdays.R

library(lubridate)

# Function to count days, weekdays and weeks in a given month
counts <- function (year, month) {
  # Get the number of days in the month
  num_days <- days_in_month(as.Date(paste(year, month, "01", sep = "-")))

  # Initialize a counter
  weekday_count <- 0
  week_count <- 0

  # Loop through each day of the month
  for (day in 1:num_days) {
    # Get the date
    date <- as.Date(paste(year, month, day, sep = "-"))

    # Check if the day is a weekday (Monday to Friday)
    if (weekdays(date) %in% c("Monday", "Tuesday", "Wednesday", "Thursday", "Friday")) {
      weekday_count <- weekday_count + 1
    }
    if (weekdays(date) == "Wednesday") {
      week_count <- week_count + 1
    }
  }

  # Return the weekday count
  return(c(num_days, weekday_count, week_count))
}

# Function to count days, weekdays and weeks per month within a given date range
counts_range <- function (start_date, end_date) {
  # Convert start and end dates to date objects
  start_date <- as.Date(start_date)
  end_date <- as.Date(end_date)

  # Get the start and end year and month
  start_year <- as.numeric(format(start_date, "%Y"))
  end_year <- as.numeric(format(end_date, "%Y"))
  start_month <- as.numeric(format(start_date, "%m"))
  end_month <- as.numeric(format(end_date, "%m"))

  # Initialize a list to store the counts per month
  counts_per_month <- list()

  # Loop through each year and month
  for (year in start_year:end_year) {
    for (month in 1:12) {
      # Check if the month is within the range
      if ((year == start_year && month < start_month) ||
          (year == end_year && month > end_month)) {
        next  # Skip the iteration if the month is outside the range
      }

      # Count weekdays for the month
      weekday_count <- counts(year, month)

      # Store the count in the list
      counts_per_month[[paste(year, month, sep = "-")]] <- weekday_count
    }
  }

  # Return the counts per month
  return(counts_per_month)
}

# Function to convert counts per month to counts per month, quarter, halfyear and year
per_q_h_y <- function (x) {
  per_quarter <- rowSums(matrix(x, length(x) / 3, byrow = T))
  per_halfyear <- rowSums(matrix(x, length(x) / 6, byrow = T))
  per_year <- rowSums(matrix(x, length(x) / 12, byrow = T))
  return(list(m = x, q = per_quarter, h = per_halfyear, y = per_year))
}

# Example usage
start_date <- "1900-01-01"
end_date <- "2100-12-31"

counts_per_month <- counts_range(start_date, end_date)

days_per_month <- unlist(lapply(counts_per_month, function (x) x[1]))
weekdays_per_month <- unlist(lapply(counts_per_month, function (x) x[2]))
weeks_per_month <- unlist(lapply(counts_per_month, function (x) x[3]))

days_per <- per_q_h_y(days_per_month)
weekdays_per <- per_q_h_y(weekdays_per_month)
weeks_per <- per_q_h_y(weeks_per_month)

days_mat <- matrix(unlist(lapply(days_per, summary)), 4, byrow = TRUE)
weekdays_mat <- matrix(unlist(lapply(weekdays_per, summary)), 4, byrow = TRUE)
weeks_mat <- matrix(unlist(lapply(weeks_per, summary)), 4, byrow = TRUE)

full_mat <- rbind(days_mat, weekdays_mat, weeks_mat)[, c(1, 4, 6)]

colnames(full_mat) <- c("Min.", "Mean", "Max.")
periodicities <- c("month", "quarter", "half-year", "year")
rownames(full_mat) <- c(paste0("Days per ", periodicities), paste0("Weekdays per ", periodicities), paste0("Weeks per ", periodicities))

print(full_mat)