Updates to cycling_route_analysis.Rmd

cycling_route_analysis.Rmd

@@ -1,5 +1,5 @@
 ---
-title: "East High Active Travel"
+title: "East High Cycling Routes"
 output:
   html_document:
     toc: true
@@ -80,23 +80,45 @@ register_stadiamaps(key = substr(read_file(file = "api_keys/stadia_api_key"), 1,
 ```
 # Analysis
 
-## Subset Addresses Within 3 Miles
+```{r analysisPreamble, eval = TRUE, echo = FALSE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
+radius <- 3 # miles
+levels <- c(1)
+res <- 100
+threshold <- 1
+```
+
+## Subset Addresses Within `r radius` Miles
 
 ```{r cycleBoundary, eval = TRUE, echo = TRUE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
-
-radius <- 3 # miles
-
 cycle_boundary_m <- radius*1609
 school_focus <- data.frame(name = c("East High School"), NCES_CODE = c("550852000925"))
+#school_focus <- data.frame(name = c("IMAP"), NCES_CODE = c("550008203085"))
 
 cycle_boundary_poly <- fill_holes(st_make_valid(osrmIsodistance(
   loc = WI_schools %>% filter(NCES_CODE %in% school_focus$NCES_CODE),
-  breaks = c(cycle_boundary_m),
+#  breaks = c(cycle_boundary_m),
-  res = 80)
+  breaks = cycle_boundary_m*levels,
-), units::set_units(1, km^2))
+  res = res)
+), units::set_units(threshold, km^2))
 
 addresses_near <- st_intersection(addresses, cycle_boundary_poly)
 ```
+Notes:
+
+- _osrmIsoDistance_ is the primary function in the above chunk.
+- This function computes areas that are reachable within a given road
+distance from a point and returns the reachable regions as
+polygons. These areas of equal travel distance are called isodistances.
+- Input is a point represented as an sf object (extended
+data.frame-like objects with a simple feature list column) could be
+other classes, e.g., vector of coods, data.frame of lat tand
+long. etc.
+- Arguments to osrmIsodistances used here are breaks and res
+ - breaks: a numeric vector of break values to define isodistance areas, in meters.
+ - res: number of points used to compute isodistances, one side of the
+square grid, the total number of points will be res*res. Increase res to obtain more detailed isodistances.
+- _fill\_holes_ is also used with a threshold of `r threshold` km^2.
+- _st\_intersection_ is also used on sf objects (simple features?)
 
 ## Calculate Routes
 
@@ -110,10 +132,12 @@ for(i in addresses_near$number) {
   message(paste0("done - ", i, "of", max(addresses_near$number)))
 }
 
-
 routes <- bind_rows(routes)
 ```
 
+Notes:
+- _osrmRoute_ is the primary function used above.
+
 
 ## Combine routes with Bike LTS
 ```{r routeslts, eval = TRUE, echo = TRUE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
@@ -127,6 +151,9 @@ bike_lts_buffer["student_use"] <- unlist(lapply(st_intersects(bike_lts_buffer, r
 bike_lts <- st_join(bike_lts, bike_lts_buffer %>% select(OBJECTID, student_use))
 ```
 
+Notes:
+
+
 # Make Maps
 
 
@@ -151,7 +178,7 @@ basemap <- get_stadiamap(bbox = bbox, zoom = 15, maptype = "stamen_toner_lite")
 ```
 
 ## Generate map of addresses
-```{r mapaddresses, eval = TRUE, echo = TRUE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
+```{r mapaddresses, eval = TRUE, echo = FALSE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
 
 ggmap(basemap) +
   labs(title = paste0("Student homes at ",
@@ -199,12 +226,12 @@ ggsave(file = paste0("figures/",
 ```
 
 ## Generate map of routes
-```{r maproutes, eval = TRUE, echo = TRUE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
+```{r maproutes, eval = TRUE, echo = FALSE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
 # generate map
 ggmap(basemap) +
   labs(title = paste0("Cycling routes for students at ",
     school_focus %>% pull(name)),
-    subtitle = "only showing routes within the ??? mile cycling boundary",
+    subtitle = paste0("only showing routes within the ", radius, " mile cycling boundary"),
     x = NULL,
     y = NULL,
     color = NULL,
@@ -250,7 +277,7 @@ ggsave(file = paste0("figures/",
 ```
 
 ## Generate map of routes with LTS
-```{r maprouteslts, eval = TRUE, echo = TRUE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
+```{r maprouteslts, eval = TRUE, echo = FALSE, results = "show", warning = FALSE, error = TRUE, message = FALSE}
 # generate map
 ggmap(basemap) +
   labs(title = paste0("Cycling routes for students at ",