Merge pull request #43 from eliocamp/dmi

Adds download_dmi to download Dipole Mode Index (#42)

NAMESPACE

@@ -2,6 +2,7 @@
 
 export(download_aao)
 export(download_ao)
+export(download_dmi)
 export(download_enso)
 export(download_mei)
 export(download_nao)

NEWS.md

@@ -5,6 +5,7 @@
 * Skip some tests on CRAN and use CI services to catch errors.
 * Removed links causing this failures:
 > Check process probably crashed or hung up for 20 minutes ... killed
+* Adds Dipole Mode Index. #42
 
 ## rsoi v0.5.3
 * Remove Extended PDO because data is no longer available. 

R/download-dmi.R

@@ -0,0 +1,81 @@
+#' @export
+#' @title Download Dipole Mode Index (DMI)
+#' 
+#' @description Intensity of the IOD is represented by anomalous SST gradient 
+#' between the western equatorial Indian Ocean (50E-70E and 10S-10N) and the 
+#' south eastern equatorial Indian Ocean (90E-110E and 10S-0N). 
+#' This gradient is named as Dipole Mode Index (DMI). 
+#' When the DMI is positive then, the phenomenon is refereed as the positive
+#' IOD and when it is negative, it is refereed as negative IOD.
+#'
+#' 
+#' @inheritParams download_oni
+#' 
+#' @return 
+#' \itemize{
+#' \item Year: Year of record
+#' \item Month: Month of record
+#' \item Date: Date object that uses the first of the month as a placeholder. Date formatted as date on the first of the month because R only supports one partial of date time
+#' \item DMI: Dipole Mode Index
+#' }
+#' 
+#' @examples
+#' \dontrun{
+#' dmi <- download_dmi()
+#' }
+#'
+#' @references \url{https://psl.noaa.gov/gcos_wgsp/Timeseries/DMI/}
+download_dmi <- function(use_cache = FALSE, file = NULL) {
+  with_cache(use_cache = use_cache, file = file, 
+             memoised = download_dmi_memoised, 
+             unmemoised = download_dmi_unmemoised, 
+             read_function = read_dmi)
+}
+
+download_dmi_unmemoised = function() {
+  dmi_link = "https://psl.noaa.gov/gcos_wgsp/Timeseries/Data/dmi.had.long.data"
+
+  res = tryCatch(
+    check_response(dmi_link),
+    error = function(e) {
+      message(e)
+      return(invisible(NULL))
+    }
+  )
+
+  years = strsplit(trimws(readLines(res, n = 1)), " ")[[1]]
+  rows = diff(as.numeric(years)) + 1
+  months = month.abb
+
+  dmi =  read.csv(check_response(dmi_link),    # reset connection
+                  header = FALSE, 
+                  col.names = c("Year", months),
+                  nrows = rows,
+                  skip = 1, 
+                  na.strings = "-9999.000",
+                  sep = "",
+                  stringsAsFactors = FALSE)
+
+  grid = expand.grid(Year = dmi$Year, Month = months)
+  grid$DMI = c(as.matrix(dmi[, months]))
+  grid$Month = factor(grid$Month, levels = months)
+  grid$Date = as.Date(paste0(grid$Year, "-", as.numeric(grid$Month) ,"-01"), "%Y-%m-%d")
+
+  grid <- grid[, c("Year", "Month", "Date", "DMI")]
+  class(grid) = c("tbl_df", "tbl", "data.frame") 
+
+  return(grid)
+}
+
+download_dmi_memoised <- memoise::memoise(download_dmi_unmemoised)
+
+
+read_dmi <- function(file) {
+  data <- read.csv(file)
+  data$Date <- as.Date(data$Date)
+  data$Month <- factor(data$Month, 
+                       levels = month.abb)
+
+  class(data) <- c("tbl_df", "tbl", "data.frame")
+  data
+}

tests/testthat/test_download_.R

@@ -1,4 +1,4 @@
-indexes <- c("oni", "ao", "nao", "soi", "mei", "npgo", "aao", "pdo")
+indexes <- c("oni", "ao", "nao", "soi", "mei", "npgo", "aao", "pdo", "dmi")
 
 context("Testing download")