From c97a4f5a9fe30ffc3321681a97eea167cfc427b5 Mon Sep 17 00:00:00 2001
From: Johannes Ranke <jranke@uni-bremen.de>
Date: Thu, 23 Jul 2020 12:22:25 +0200
Subject: PEC_sw_drift: Rautmann formula (1 app, Ackerbau)

This makes it possible to calculate drift PECsw for other distances than
present in the JKI data or the Rautmann paper.
---
 R/PEC_sw_drift.R | 43 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 11 deletions(-)

(limited to 'R')

diff --git a/R/PEC_sw_drift.R b/R/PEC_sw_drift.R
index 6fcaecf..2dfd651 100644
--- a/R/PEC_sw_drift.R
+++ b/R/PEC_sw_drift.R
@@ -8,7 +8,9 @@
 #' @param applications Number of applications for selection of drift percentile
 #' @param drift_percentages Percentage drift values for which to calculate PECsw.
 #'   'drift_data' and 'distances' if not NULL.
-#' @param drift_data Source of drift percentage data
+#' @param drift_data Source of drift percentage data. If 'JKI', the [drift_data_JKI]
+#'   included in the package is used. If 'RF', the Rautmann formula is used, if
+#'   implemented for the crop type and number of applications
 #' @param crop Crop name (use German names for JKI data), defaults to "Ackerbau"
 #' @param distances The distances in m for which to get PEC values
 #' @param water_depth Depth of the water body in cm
@@ -19,15 +21,23 @@
 #' @author Johannes Ranke
 #' @examples
 #' PEC_sw_drift(100)
-PEC_sw_drift <- function(rate, 
-                         applications = 1,
-                         water_depth = 30, 
-                         drift_percentages = NULL,
-                         drift_data = "JKI",
-                         crop = "Ackerbau",
-                         distances = c(1, 5, 10, 20),
-                         rate_units = "g/ha",
-                         PEC_units = "\u00B5g/L")
+#' # Alternatively, we can use the formula for a single application to "Ackerbau" from the paper
+#' PEC_sw_drift(100, drift_data = "RF")
+#'
+#' # This makes it possible to also use different substances
+#' PEC_sw_drift(100, distances = c(1, 3, 5, 6, 10, 20, 50, 100), drift_data = "RF")
+#'
+#' # Using custom drift percentages is also supported
+#' PEC_sw_drift(100, drift_percentages = c(2.77, 0.95, 0.57, 0.48, 0.29, 0.15, 0.06, 0.03))
+PEC_sw_drift <- function(rate,
+  applications = 1,
+  water_depth = 30,
+  drift_percentages = NULL,
+  drift_data = c("JKI", "RF"),
+  crop = "Ackerbau",
+  distances = c(1, 5, 10, 20),
+  rate_units = "g/ha",
+  PEC_units = "\u00B5g/L")
 {
   rate_units <- match.arg(rate_units)
   PEC_units <- match.arg(PEC_units)
@@ -36,8 +46,19 @@ PEC_sw_drift <- function(rate,
   PEC_sw_overspray <- rate * 1e6 / water_volume          # in µg/L
   dist_index <- as.character(distances)
 
+  RF <- list(
+    "1" = list("Ackerbau" = function(distance) 2.7705 * distance^-0.9787) # p. 134
+  )
+  if (drift_data == "RF") {
+    if (is.null(RF[[as.character(applications)]])) stop("Rautmann formula not included for ", applications, " applications")
+    if (is.null(RF[[as.character(applications)]][[crop]])) stop("Rautmann formula not included for this case")
+  }
+
   if (is.null(drift_percentages)) {
-    drift_percentages <- pfm::drift_data_JKI[[applications]][dist_index, crop]
+    drift_percentages <- switch(drift_data,
+      JKI = pfm::drift_data_JKI[[applications]][dist_index, crop],
+      RF =  RF[[applications]][[crop]](distances)
+    )
     names(drift_percentages) <- paste(dist_index, "m")
   } else {
     names(drift_percentages) <- paste(drift_percentages, "%")
-- 
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