Address Issue #44, added D0 as its own variable to ensure FBP reports…

… an effective date of minimum foliar moisture.

DESCRIPTION

@@ -42,4 +42,4 @@ Suggests:
 Config/testthat/edition: 3
 Encoding: UTF-8
 LazyData: true
-RoxygenNote: 7.2.3
+RoxygenNote: 7.3.1

R/fire_behaviour_prediction.r

@@ -272,12 +272,15 @@ fire_behaviour_prediction <- function(
   }
   CBH <- crown_base_height(FUELTYPE, CBH, SD, SH)
   CFL <- crown_fuel_load(FUELTYPE, CFL)
+  D0 <- ifelse(D0 <= 0, foliar_moisture_content_minimum(LAT, LONG, ELV, DJ, D0), D0)
   FMC <- ifelse(
     FMC <= 0 | FMC > 120 | is.na(FMC),
     foliar_moisture_content(LAT, LONG, ELV, DJ, D0),
     FMC
   )
+
   FMC <- ifelse(FUELTYPE %in% c("D1", "S1", "S2", "S3", "O1A", "O1B"), 0, FMC)
+
   ############################################################################
   #                         END
   ############################################################################

R/foliar_moisture_content.r

@@ -17,48 +17,39 @@
 #' @noRd
 
 foliar_moisture_content <- function(LAT, LONG, ELV, DJ, D0) {
-  # Initialize vectors
-  FMC <- rep(-1, length(LAT))
-  LATN <- rep(0, length(LAT))
-  # Calculate Normalized Latitude
-  # Eqs. 1 & 3 (FCFDG 1992)
-  LATN <- ifelse(
-    D0 <= 0,
-    ifelse(
-      ELV <= 0,
-      46 + 23.4 * exp(-0.0360 * (150 - LONG)),
-      43 + 33.7 * exp(-0.0351 * (150 - LONG))
-    ),
-    LATN
-  )
-  # Calculate Date of minimum foliar moisture content
-  # Eqs. 2 & 4 (FCFDG 1992)
-  D0 <- ifelse(
-    D0 <= 0,
-    ifelse(
-      ELV <= 0,
-      151 * (LAT / LATN),
-      142.1 * (LAT / LATN) + 0.0172 * ELV
-    ),
-    D0
-  )
-  # Round D0 to the nearest integer because it is a date
-  D0 <- round(D0, 0)
+
+  D0 <- foliar_moisture_content_minimum(LAT, LONG, ELV, DJ, D0)
+
   # Number of days between day of year and date of min FMC
+
   # Eq. 5 (FCFDG 1992)
+
   ND <- abs(DJ - D0)
+
   # Calculate final FMC
+
   # Eqs. 6, 7, & 8 (FCFDG 1992)
+
   FMC <- ifelse(
+
     ND < 30,
+
     85 + 0.0189 * ND^2,
+
     ifelse(
+
       ND >= 30 & ND < 50,
+
       32.9 + 3.17 * ND - 0.0288 * ND^2,
+
       120
+
     )
+
   )
+
   return(FMC)
+
 }
 
 .FMCcalc <- function(...) {

R/foliar_moisture_content_minimum.r

@@ -0,0 +1,59 @@
+#' Foliar Moisture Content Minimum Calculator
+#'
+#' @description Calculate date of Foliar Moisture Content Minimum.
+#' All variables names are laid out in the same manner as Forestry Canada
+#' Fire Danger Group (FCFDG) (1992). Development and Structure of the
+#' Canadian Forest Fire Behavior Prediction System." Technical Report
+#' ST-X-3, Forestry Canada, Ottawa, Ontario.
+#'
+#' @param LAT    Latitude (decimal degrees)
+#' @param LONG   Longitude (decimal degrees)
+#' @param ELV    Elevation (metres)
+#' @param DJ     Day of year (offeren referred to as julian date)
+#' @param D0     Date of minimum foliar moisture content. _If D0, date of min
+#'                   FMC, is not known then D0 = NULL._
+#'
+#' @return D0: Date of minimum foliar moisture content
+#' @noRd
+
+foliar_moisture_content_minimum <- function(LAT, LONG, ELV, DJ, D0) {
+
+  # Initialize vectors
+
+  FMC <- rep(-1, length(LAT))
+  LATN <- rep(0, length(LAT))
+
+  # Calculate Normalized Latitude
+
+  # Eqs. 1 & 3 (FCFDG 1992)
+
+  LATN <- ifelse(
+    D0 <= 0,
+    ifelse(
+      ELV <= 0,
+      46 + 23.4 * exp(-0.0360 * (150 - LONG)),
+      43 + 33.7 * exp(-0.0351 * (150 - LONG))
+    ),
+    LATN
+  )
+
+  # Calculate Date of minimum foliar moisture content
+
+  # Eqs. 2 & 4 (FCFDG 1992)
+
+  D0 <- ifelse(
+    D0 <= 0,
+    ifelse(
+      ELV <= 0,
+      151 * (LAT / LATN),
+      142.1 * (LAT / LATN) + 0.0172 * ELV
+    ),
+    D0
+  )
+
+  # Round D0 to the nearest integer because it is a date
+
+  D0 <- round(D0, 0)
+  return(D0)
+
+}