Close #65

R/uptake.R

@@ -118,20 +118,42 @@ uptake_pct_govtarget = function(
 #' @inheritParams uptake_pct_govtarget
 #' @export
 #' @examples
+#' # https://www.jtlu.org/index.php/jtlu/article/downloadSuppFile/862/360)
+#' # Equation 1B:
+#' distance = 15
+#' gradient = 2
+#' logit = -3.959 + 2.523 +
+#'   ((-0.5963 - 0.07626) * distance) +
+#'   (1.866 * sqrt(distance)) +
+#'   (0.008050 * distance^2) +
+#'   (-0.2710 * gradient) +
+#'   (0.009394 * distance*gradient) +
+#'   (-0.05135 * sqrt(distance) *gradient)
+#' logit
+#' # Result: -3.144098
+#'
+#' pcycle = exp(logit) / (1 + exp(logit))
+#' # Result: 0.04132445
+#' boot::inv.logit(logit)
+#' uptake_pct_godutch(distance, gradient, alpha = -3.959 + 2.523, d1 = -0.5963 - 0.07626,
+#'  d2 = 1.866, d3 = 0.008050, h1 = -0.2710, i1 = 0.009394, i2 = -0.05135
+#' )
+#' # these are the default values
+#' uptake_pct_godutch(distance, gradient)
 #' l = routes_fast_leeds
 #' pcycle_scenario = uptake_pct_godutch(l$length, l$av_incline)
 #' plot(l$length, pcycle_scenario)
 uptake_pct_godutch = function(
   distance,
   gradient,
-  alpha = -3.959,
-  d1 = -0.5963,
-  d2 = 1.832,
-  d3 = 0.007956,
-  h1 = -0.2872,
-  i1 = 0.01784,
-  i2 = -0.09770
-) {
+  alpha = -3.959 + 2.523,
+  d1 = -0.5963 - 0.07626,
+  d2 = 1.866,
+  d3 = 0.008050,
+  h1 = -0.2710,
+  i1 = 0.009394,
+  i2 = -0.05135
+  ) {
   if(!exists(c("distance", "gradient")) |
      !is.numeric(c(distance, gradient))) {
     stop("distance and gradient need to be numbers.")
@@ -141,14 +163,12 @@ uptake_pct_godutch = function(
     message("Distance assumed in m, switching to km")
     distance = distance / 1000
   }
-  pcycle_scenario = alpha + (d1 * distance) +
+  logit_pcycle = alpha + (d1 * distance) +
     (d2 * sqrt(distance) ) + (d3 * distance^2) +
     (h1 * gradient) +
     (i1 * distance * gradient) +
     (i2 * sqrt(distance) * gradient)
-  # looks like this
-  pcycle_scenario = pcycle_scenario + 2.499 -0.07384 * distance
-  boot::inv.logit(pcycle_scenario)
+  boot::inv.logit(logit_pcycle)
 }