README.Rmd

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output: github_document
---

# Extra 'sf' Simple Features manipulations

[![CRAN](http://www.r-pkg.org/badges/version/sfx)](https://cran.r-project.org/package=sfx)
[![Lifecycle: experimental](https://img.shields.io/badge/lifecycle-experimental-red.svg)](https://www.tidyverse.org/lifecycle/#experimental)
[![License](http://img.shields.io/badge/license-GPL%20%28%3E=%202%29-brightgreen.svg?style=flat)](http://www.gnu.org/licenses/gpl-2.0.html)

Still a work-in-progress -- I want to add a few more features, such as:
  
  * Random density points (random points with density values? why? guassian distribution for sampling?)
  * Alternative density methods.
  

See the [Reference section][ref_sec] for detailed examples.

[ref_sec]: http://seasmith.github.io/packages/sfx/reference/index.html

```{r, collapse=TRUE}
library(sf)
library(sfx)
library(ggplot2)
library(stars) # for geom_stars() 

olinda1 <- sf::read_sf(system.file("shape/olinda1.shp", package = "sf"))

olinda1_centroids <- olinda1  %>%
    sf::st_centroid()
```

## Point
```{r}
# MASS::kde2d kernel (default)
olinda1_centroids %>%
    st_density() %>%
    ggplot() +
    geom_sf(data = olinda1, fill = NA, color = "gray80") +
    geom_sf(aes(color = density)) +
    scale_color_viridis_c() +
    theme_void()

# KernSmooth::bkde2D kernel
olinda1_centroids %>%
    st_density(method = "bkde2D") %>%
    ggplot() +
    geom_sf(data = olinda1, fill = NA, color = "gray80") +
    geom_sf(aes(color = density)) +
    scale_color_viridis_c() +
    theme_void()
```

## Grid
```{r}
# n = 10 produces a 10x10 grid
olinda1_centroids %>%
    st_density(return_geometry = "grid", n = 10) %>%
    ggplot() +
    geom_sf(data = olinda1, fill = NA, color = "gray80") +
    geom_sf(aes(color = density)) +
    scale_color_viridis_c() +
    theme_void()
```

## Isoband
```{r}
olinda1_centroids %>%
    st_density(return_geometry = "isoband") %>%
    ggplot() +
    geom_sf(aes(fill = level), alpha = 1) +
    geom_sf(data = olinda1_centroids, color = "red", size = 2) +
    scale_fill_viridis_c()
```

## Raster
```{r, eval=TRUE}
# NOT WORKING AS EXPECTED
olinda1_centroids %>%
    st_density(return_geometry = "raster", n = 50) %>%
    # use lambda expr to place . inside geom_stars
    # or else ggplot() will error on fortify() attempt
    {
      ggplot() +
        geom_stars(data = .) +
        coord_equal() +
        theme_void() +
        scale_fill_viridis_c() +
        scale_x_discrete(expand = c(0, 0)) +
        scale_y_discrete(expand = c(0, 0))
    }
```

## Current Functions

```{r, eval=FALSE}
# Density estimation (kernel based)
st_density

# Joins
st_inner_join
st_left_join
st_anti_join
st_semi_join

# Convert logical matrix to logical vector
st_any

# Binary logical helpers
st_any_contains
st_any_contains_properly
st_any_covered_by
st_any_covers
st_any_crosses
st_any_disjoint
st_any_equals
st_any_equals_exact
st_any_intersects
st_any_is_within_distance
st_any_overlaps
st_any_touches
st_any_within

# Unitless dimensions
st_ul_area
st_ul_distance
st_ul_length

# Bounding-box helpers
st_extent
st_xdist
st_ydist
st_xlim
st_ylim
```

## Future Functions?

```{r, eval=FALSE}
geom_sf_density()
plot_sf_density()
```