From c3d2280af8928000288ff864a271835a533448f4 Mon Sep 17 00:00:00 2001
From: Ben Letham <bletham@gmail.com>
Date: Wed, 11 Oct 2017 09:38:15 -0700
Subject: [PATCH] Add layer_changepoints from #273

---
 R/NAMESPACE                 |  1 +
 R/R/utils.R                 | 33 +++++++++++++++++++++++++++++++++
 R/man/layer_changepoints.Rd | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+)
 create mode 100644 R/R/utils.R
 create mode 100644 R/man/layer_changepoints.Rd

diff --git a/R/NAMESPACE b/R/NAMESPACE
index 415e5a9..6a5312a 100644
--- a/R/NAMESPACE
+++ b/R/NAMESPACE
@@ -6,6 +6,7 @@ export(add_regressor)
 export(add_seasonality)
 export(cross_validation)
 export(fit.prophet)
+export(layer_changepoints)
 export(make_future_dataframe)
 export(plot_forecast_component)
 export(predictive_samples)
diff --git a/R/R/utils.R b/R/R/utils.R
new file mode 100644
index 0000000..2116e91
--- /dev/null
+++ b/R/R/utils.R
@@ -0,0 +1,33 @@
+#' Get layers to overlay significant changepoints on prophet forecast plot.
+#'
+#' @param m Prophet model object.
+#' @param threshold Numeric, changepoints where abs(delta) >= threshold are
+#'  significant. (Default 0.01)
+#' @param cp_color Character, line color. (Default "red")
+#' @param cp_linetype Character or integer, line type. (Default "dashed")
+#' @param trend Logical, if FALSE, do not draw trend line. (Default TRUE)
+#' @param ... Other arguments passed on to layers.
+#'
+#' @return A list of ggplot2 layers.
+#'
+#' @examples
+#' \dontrun{
+#' plot(m, fcst) + layer_changepoints(m)
+#' }
+#'
+#' @export
+layer_changepoints <- function(m, threshold = 0.01, cp_color = "red",
+                               cp_linetype = "dashed", trend = TRUE, ...) {
+  layers <- list()
+  if (trend) {
+    trend_layer <- ggplot2::geom_line(
+      ggplot2::aes_string("ds", "trend"), color = cp_color, ...)
+    layers <- append(layers, trend_layer)
+  }
+  signif_changepoints <- m$changepoints[abs(m$params$delta) >= threshold]
+  cp_layer <- ggplot2::geom_vline(
+    xintercept = as.integer(signif_changepoints), color = cp_color,
+    linetype = cp_linetype, ...)
+  layers <- append(layers, cp_layer)
+  return(layers)
+}
diff --git a/R/man/layer_changepoints.Rd b/R/man/layer_changepoints.Rd
new file mode 100644
index 0000000..674c717
--- /dev/null
+++ b/R/man/layer_changepoints.Rd
@@ -0,0 +1,35 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/utils.R
+\name{layer_changepoints}
+\alias{layer_changepoints}
+\title{Get layers to overlay significant changepoints on prophet forecast plot.}
+\usage{
+layer_changepoints(m, threshold = 0.01, cp_color = "red",
+  cp_linetype = "dashed", trend = TRUE, ...)
+}
+\arguments{
+\item{m}{Prophet model object.}
+
+\item{threshold}{Numeric, changepoints where abs(delta) >= threshold are
+significant. (Default 0.01)}
+
+\item{cp_color}{Character, line color. (Default "red")}
+
+\item{cp_linetype}{Character or integer, line type. (Default "dashed")}
+
+\item{trend}{Logical, if FALSE, do not draw trend line. (Default TRUE)}
+
+\item{...}{Other arguments passed on to layers.}
+}
+\value{
+A list of ggplot2 layers.
+}
+\description{
+Get layers to overlay significant changepoints on prophet forecast plot.
+}
+\examples{
+\dontrun{
+plot(m, fcst) + layer_changepoints(m)
+}
+
+}