In jr-packages/jrSpatial: Jumping Rivers: Spatial Data Analysis using R

Question 1 - reading in data

First let's load the required libraries

library("sf")
library("jrSpatial")

We're going to get you to read in some data, but first you need some data to read in! Running the following function from the jrSpatial package will copy a folder into your current working directory containing shape files

get_ukgeom()

1. Using st_read(), read the shape file in to R r ukgeom = st_read("ukgeom/ukgeom.shp") r data(ukgeom, package = "jrSpatial")

2. Plot the data r plot(ukgeom)

3. Plot the data, but this time only showing the plots for the population in 2015 and 2017 r plot(ukgeom[, c("pop_2015", "pop_2017")])

Question 2a - cooking with sf

sf objects are built very differently to normal R objects, such as a vector or tibble. So in this question we're going to get you to build up a couple of them from scratch.

We'll go through the 7 types of simple features objects. Have a go at running the code for each object, then at the end we'll give you a few questions.

1. Point. You can make a sf point using st_point() r p = st_point(c(13, 15)) plot(p)

2. Multipoint. This is one sf object that contains multiple points. Before converting it to a multipoint object the points need to be a matrix. Where each row is a point r ps = rbind(c(10, 10), c(10, 9), c(11, 9), c(11, 10)) mp = st_multipoint(ps) plot(mp)

3. Linestring. This is several points joined up to make a line. We can convert a multipoint to a linestring easily using st_linestring() r l = st_linestring(mp) plot(l)

4. Multilinestring. This is one sf object that contains multiple separate lines. Use sf_multilinestring() to create these. Notice the lines have to be in a list r ps2 = rbind(c(11, 11), c(12, 11)) mls = st_multilinestring(list(ps, ps2)) plot(mls)

5. Polygon. This is a shape. On a map you'd think of this as a country or island. Use st_polygon() to create a polygon. Again, in a list! r pol_points = rbind(c(10, 10), c(10, 9), c(11, 9), c(11, 10), c(10, 10)) pol = st_polygon(list(pol_points)) plot(pol)

6. Multipolygon. This is one sf object containing multiple polygons. The function used is st_multipolygon() and each polygon is within it's own list, inside another list. r pol_points2 = rbind(c(12, 12), c(13, 13), c(14, 12), c(12, 12)) mpol = st_multipolygon(list(list(pol_points), list(pol_points2))) plot(mpol)

7. Geometry collection. This is an sf object that can be made up of all the previous 6 objects, made with st_geometrycollection() r gc = st_geometrycollection(list(p, mpol, mls)) plot(gc)

Question 2b - cooking with sf

1) Hurricane Shary hit the Americas in October 2010. We've managed to attain the approximate longitude and latitude for the storm every 6 hours it was active. To get you started, I've created the matrix of longitudes and latitudes. Turn the matrix into a sf linestring and plot it r longitude = c(-61, -63, -65, -66, -66) latitude = c(26, 27, 28, 29, 30) shary_matrix = cbind(longitude, latitude) r shary = st_linestring(shary_matrix) plot(shary)

| Longitude | Latitude | |----------- |---------- | | -64 | 31 | | -61 | 33 | | -57 | 35 |

2) 12 hours after Shary was declassified to a tropical storm, it was upgraded again to a hurricane. You can see this data the table. Create a matrix called shary_matrix2, using code similar to that of question 1. Combine the two matrices shary_matrix and shary_matrix2 into a multilinestring r longitude2 = c(-64, -61, -57) latitude2 = c(31, 33, 35) shary_matrix2 = cbind(longitude2, latitude2) shary = st_multilinestring(list(shary_matrix, shary_matrix2))

3) Hurrican Colin hit America in August of 2010. Below is the code to turn storm Colin longitude and latitude into a sf linestring r longitude = c(-65, -66, -67, -67, -66) latitude = c(23, 24, 25, 26, 27) colin_matrix = cbind(longitude, latitude) colin = st_linestring(colin_matrix)

4) Ideally we'd like to keep all of these inside of a data.frame with one column containing the geometry. Just like uk_shape. We can do this using st_sf() and st_sfc() r hurricane = st_sf(name = c("Shary", "Colin"), geometry = st_sfc(shary, colin)) Try plotting hurricane, what happens?

jr-packages/jrSpatial documentation built on Sept. 23, 2020, 2:31 p.m.