---

title: "tmap example: choropleth (World)"

output:

bookdown::html_vignette2:

pkgdown:

as_is: true

template:

math-rendering: mathjax

bibliography: '`r system.file("tmap.bib", package="tmap")`'

csl: "`r system.file('ieee.csl', package = 'tmap')`"

editor_options:

chunk_output_type: console

---

```{r, include = FALSE}

knitr::opts_chunk$set(

collapse = TRUE,

out.width = "100%",

dpi = 300,

fig.width = 7.2916667,

comment = "#>"

)

hook_output <- knitr::knit_hooks$get("output")

knitr::knit_hooks$set(output = function(x, options) {

lines <- options$output.lines

if (is.null(lines)) {

return(hook_output(x, options)) # pass to default hook

}

x <- unlist(strsplit(x, "\n"))

more <- "..."

if (length(lines)==1) { # first n lines

if (length(x) > lines) {

# truncate the output, but add ....

x <- c(head(x, lines), more)

}

} else {

x <- c(more, x[lines], more)

}

# paste these lines together

x <- paste(c(x, ""), collapse = "\n")

hook_output(x, options)

})

```

```{r, message = FALSE}

library(tmap)

library(dplyr)

library(sf)

tmap_options(scale = 0.75)

```

## About the data

A spatial data object contained in tmap is called `World`. It is a data frame with a row for each country. The columns are the following data variables plus an additional geometry column which contains the geometries (see sf package):

```{r}

names(World)

```

We will create a choropleth of the Gender Inequality Index (GII) per country.

## The choropleth: step 1

```{r, fig.height = 4}

tm_shape(World) +

tm_polygons(fill = "gender")

```

## The choropleth: step 2

A few improvements:

* A suitable map projection. This one 'Equal Earth' is equal-area, i.e. the polygon area sizes are proportianal to the real-world country area sizes.

* A different color scheme. Run `cols4all::c4a_gui()` to explore them. For this application, we were looking for: a diverging, color-blind friendly palette with sufficient contrast with black (to see the border lines)

* A custom legend title

* The option `earth_boundary` is enabled, which shows the earth boundaries. Note that this feature is only available for certain map projections (for advanced users: families of pseudo-cylindrical and orthographic projections).

* The legend box is placed on top of the map, on the left bottom.

```{r, fig.height = 5}

tm_shape(World, crs = "+proj=eqearth") +

tm_polygons(

fill = "gender",

fill.scale = tm_scale_intervals(values = "-tableau.classic_orange_blue"),

fill.legend = tm_legend(

"Gender Inequality Index (GII)",

position = tm_pos_on_top(pos.h = "left", pos.v = "bottom"),

bg.color = "white")) +

tm_options(earth_boundary = TRUE, frame = FALSE)

```