Update stplanr slides

Author: Robinlovelace

vignettes/stplanr-example.Rmd

@@ -1,20 +1,14 @@
 ---
-title: "**stplanr**: A package for transport planning"
+title: "An introduction to **stplanr**: A package for transport planning"
 author: "Robin Lovelace, University of Leeds, [ITS](www.its.leeds.ac.uk/)/[LIDA](http://www.lida.leeds.ac.uk/)"
-date: "`r Sys.Date()"
+date: "`r Sys.Date()`"
 output:
   ioslides_presentation:
     transition: slower
 logo: ../figure/its-logo-square.png
 ---
 
-```{r, include=FALSE}
-library(stplanr)
-library(sp) # needed for geographical objects
-library(leaflet) # needed for plotting data
-```
-
-## Talk structure
+## Contents
 
 > - Background
 > - Using stplanr
@@ -24,9 +18,9 @@ library(leaflet) # needed for plotting data
 
 ## Why **stplanr**
 
-- I became lead developer of national research project funded by the Department for Transport
-- To create the **Propensity to Cycle Tool** (PCT)
+- Contracted to create the **Propensity to Cycle Tool** (PCT)
 - Best way to understand **stplanr** is via a live demo, at **[www.pct.bike](http://www.pct.bike/)**
+- Needed functions to work with origin-destination data and routing services
 
 ```{r, echo=FALSE}
 knitr::include_graphics("https://github.com/npct/pct/raw/master/flow-model/od-data-leeds.png")
@@ -62,10 +56,14 @@ it can be loaded in with `library()`:
 
 ```{r, eval=FALSE}
 install.packages("stplanr") # stable CRAN version
-devtools::install_github("ropensci/stplanr") # dev version
-library(stplanr)
+# devtools::install_github("ropensci/stplanr") # dev version
+```
+
+```{r}
+library(stplanr) # also loads spatial package
 ```
 
+
 > - Dev version requires rtools on Windows
 
 ## Why host on ROpenSci?
@@ -126,7 +124,45 @@ data("cents", package = "stplanr")
 as.data.frame(cents[1:3,-c(3,4)])
 ```
 
-## Creating 'desire lines'
+## Creating a single desire line
+
+```{r}
+flow_single_line = flow[4,] # select only the first line
+desire_line_single = od2line(flow = flow_single_line, zones = cents)
+plot(cents)
+plot(desire_line_single, add = T)
+```
+
+## What just happened?
+
+- We selected a single 'od-pair' (`flow[4,]`)
+- The function `od2line()` matched the cents matching the lines and created a line (the hard bit)
+- How? Check the source code!
+
+```{r}
+od2line
+```
+
+## A hard-coded version:
+
+```{r}
+o = cents[cents$geo_code %in% flow$Area.of.residence[4],]
+d = cents[cents$geo_code %in% flow$Area.of.workplace[4],]
+l_single = Lines(list(Line(rbind(o@coords, d@coords))), ID = 1)
+l_sp = SpatialLines(LinesList = list(l_single))
+```
+
+## Visualising the result
+
+```{r}
+plot(cents)
+points(o, cex = 5)
+points(d, cex = 5)
+flow[4, 1:3]
+plot(l_sp, add = TRUE)
+```
+
+## Creating 'desire lines' for all flows
 
 ```{r, warning=FALSE}
 l <- od2line(flow = flow, zones = cents)
@@ -201,4 +237,22 @@ devtools::install_github("ropensci/stplanr")
 - Create issues on our [issue tracker](https://github.com/ropensci/stplanr/issues)
 - Check out the [vignette](https://cran.r-project.org/web/packages/stplanr/vignettes/introducing-stplanr.html)
 - See my tutorial on visualising spatial data for eRum: [Creating-maps-in-R/blob/master/vignettes/vspd-base-shiny.md](https://github.com/Robinlovelace/Creating-maps-in-R/blob/master/vignettes/vspd-base-shiny.md)
-- Academic paper on the PCT: http://arxiv.org/abs/1509.04425
+- Academic paper on the PCT: http://arxiv.org/abs/1509.04425
+
+## Exercises
+
+- Work through the [vignette](https://cran.r-project.org/web/packages/stplanr/vignettes/introducing-stplanr.html) provided by:
+
+```{r, eval=FALSE}
+vignette("introducing-stplanr")
+```
+
+- Create a single desire line for the 12th flow without using **stplanr** code (**stplanr** solution below):
+
+```{r, eval=FALSE}
+od2line(flow = flow[12,], zones = cents)
+```
+
+- Visualise the `flowlines` object using **tmap** with different colours and widths
+- Create a 'oneway' version of the `flowlines` and visualise these (tricky)
+- Create a **sf** version of the `flowlines` object (advanced)