---
title: "Calculate distances"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{calculate-distances}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

```{r setup}
library(GeoDist)
library(raster)
library(sp)
```

```{r, out.width="80%", fig.width=7, fig.height=7}
crs_merc <- "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m"
# Create raster
r <- raster(ncol = 20, nrow = 20,
            crs = crs_merc)
values(r) <- 1
values(r)[125:127] <- NA
values(r)[145:147] <- NA
values(r)[165:167] <- NA
plot(r)

# Create points
from_coords <- cbind(-150, 40)
from_sp <- SpatialPointsDataFrame(coords = from_coords, 
                                  data = data.frame(label = "start"),
                                  proj4string = CRS(crs_merc))

to_coords <- matrix(c(50, 0, 100, -50), byrow = TRUE, ncol = 2)
to_sp <- SpatialPointsDataFrame(coords = to_coords, 
                                data = data.frame(label = c("end1", "end2")),
                                proj4string = CRS(crs_merc))


plot(r)
points(from_sp, pch = 20, col = "blue")
points(to_sp, pch = 20, col = "red")

# For "from" and "to" being SpatialPoints
allpath <- dist.obstacle(from = from_sp, to = to_sp, r.ref = r, keep.path = TRUE)

# All path from "from[1,]" to all "to"
lines(allpath$listLines)
```