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2.2 KiB
2.2 KiB
---
output: rmarkdown::github_document
editor_options:
chunk_output_type: console
---
# terminator
Compute Global Terminator (Day/Night) Bands
## Description
Compute global terminator (day/night) bands which can be overlayed as day and night regions on a ggplot2 world map.
This is an Rcpp port of a [pure R port](https://github.com/JoGall/terminator) (by @JoGall) of a JS leaflet plugin.
## What's Inside The Tin
The following functions are implemented:
- `terminator`: Compute a single termiantor band
- `terminator_lat_lon`: Generate a full set of terminator frames
## Installation
```{r eval=FALSE}
devtools::install_github("hrbrmstr/terminator")
```
```{r message=FALSE, warning=FALSE, error=FALSE, include=FALSE}
options(width=120)
```
## Usage
(NOTE: If you're trying to just knit this Rmd, remove the `eval=FALSE` bits. I didn't want to keep generating things and was too impatient to wait for a `cache=TRUE` run).
```{r message=FALSE, warning=FALSE, error=FALSE}
library(terminator)
library(ggplot2)
library(gganimate) # devtools::install_github("dgrtwo/gganimate")
# current verison
packageVersion("terminator")
```
Joe had an asesome idea and made a perfectly fine pure R port. This one is just a wee bit faster.
```{r bench, eval=FALSE}
microbenchmark::microbenchmark(
pure_r = pure_r_terminator(as.POSIXct(Sys.Date()) + (60*60*0), -180, 190, 0.5),
rcpp = terminator::terminator(as.POSIXct(Sys.Date()) + (60*60*0), -180, 190, 0.5),
times=100
) -> mb
mb
## Unit: microseconds
## expr min lq mean median uq max neval
## pure_r 178131.642 196554.32 206498.7256 204881.1060 214984.7260 339901.567 100
## rcpp 493.219 642.67 752.3545 747.8535 828.3085 1044.269 100
```
Using Joe's animation example:
```{r anim, eval=FALSE}
term_seq <- terminator_lat_lon()
chart <- ggplot(term_seq, aes(frame = frame)) +
borders("world", colour = "gray90", fill = "gray85") +
geom_ribbon(aes(lat, ymax = lon), ymin = 90, alpha = 0.2) +
coord_equal(xlim = c(-180, 190), ylim = c(-58, 85), expand = 0) +
ggthemes::theme_map()
gganimate(
chart,
interval = 0.1, ani.width=1000, ani.height=600,
filename = "terminator-animation.gif"
)
```
