Help for package extRatum

Title:

Summary Statistics for Geospatial Features

Version:

1.0.4

Description:

Provides summary statistics of local geospatial features within a given geographic area. It does so by calculating the area covered by a target geospatial feature (i.e. buildings, parks, lakes, etc.). The geospatial features can be of any type of geospatial data, including point, polygon or line data.

License:

MIT + file LICENSE

Depends:

R (≥ 3.3.0)

Encoding:

UTF-8

LazyData:

true

RoxygenNote:

7.1.1

SystemRequirements:

C++11, GDAL (>= 2.0.1), GEOS (>= 3.4.0), PROJ (>= 4.8.0)

Date/Publication:

2021-01-18 16:50:12 UTC

Imports:

sf (≥ 0.9.5), dplyr (≥ 1.0.0), tidyr (≥ 1.1.0)

NeedsCompilation:

Packaged:

2021-01-17 07:07:47 UTC; User

Author:

Nikos Patias

[aut, cre], Francisco Rowe [aut]

Maintainer:

Nikos Patias <n.patias@liverpool.ac.uk>

Repository:

CRAN

Areal data calculation

Description

Computes three different summary statistics: (1) TotalArea total area of each polygon; (2) AreaCovered area covered by a multipolygon object within a high order polygon; and, (3) Ratio ratio between AreaCovered and TotalArea i.e. ratio between an area covered by a given set of features and total area of a higher-order geography polygon.

Usage

areal_calc(polygon_layer, higher_geo_lay, unique_id_code, crs)

Arguments

polygon_layer

multipolygon object of class sf, sfc or sfg.

higher_geo_lay

multipolygon object of class sf, sfc or sfg.

unique_id_code

a string; indicating a unique ID column of higher_geo_lay, used as the summary areas.

crs

coordinate reference system: integer with the EPSG code, or character based on proj4string.

Details

The function requires two sets of polygon data: high-order and low-order geographic polygons

Value

a tibble data frame object containing four columns is returned:

the unique_id_code of higher_geo_lay
the total area of each polygon in higher_geo_lay (TotalArea),
the total area covered by polygon_layer features (AreaCovered),
the ratio between the total area covered by polygon_layer and total area of higher_geo_lay polygon (Ratio).

Examples

## Run areal_calc() using the packages' dummy data sets.
## The data sets are georeferenced on wgs84. However, a planar system is used to measure areas.
## For the examples provided here, points and polygons relate to the United Kingdom.
## So the British National Grid is used.

## Not run:
#outcome <- areal_calc(polygon_layer = pol_small,
#higher_geo_lay = pol_large,
#unique_id_code = "large_pol_",
#crs = "epsg:27700")
## End(Not run)

Line data calculation

Description

Computes three different summary statistics: (1) TotalArea total area of each polygon; (2) TotalLength total length of a multilinestring object within a polygon (3) Ratio ratio between TotalLength and TotalArea i.e. the ratio between the total length and total area of a higher-order geography polygon.

Usage

line_calc(line_layer, higher_geo_lay, unique_id_code, crs)

Arguments

line_layer

multilinestring object of class sf, sfc or sfg.

higher_geo_lay

multipologon object of class sf, sfc or sfg.

unique_id_code

a string; indicating a unique ID column of higher_geo_lay, used as the summary areas.

crs

coordinate reference system: integer with the EPSG code, or character based on proj4string.

Value

a tibble data frame object containing four columns:

the unique_id_code of higher_geo_lay

the total area of each polygon in higher_geo_lay (TotalArea)

the total length of line_layer features (TotalLength)

the ratio between the total length of line_layer and the the total area of higher_geo_lay polygon (Ratio).

Examples

## Run line_calc() using the packages' dummy data sets.
## The data sets are georeferenced on wgs84. However, a planar system is used to measure areas.
## For the examples provided here, points and polygons relate to the United Kingdom.
## So the British National Grid is used.

## Not run:
#outcome <- line_calc(
# line_layer = lines,
# higher_geo_lay = pol_large,
# unique_id_code = "large_pol_",
# crs = "epsg:27700")
## End(Not run)

Line geospatial layer.

Description

Toy dataset of line data.

Usage

lines

Format

A geospatial file of six lines georeferenced in wgs84.

Source

Own dataset.

Point data calculation

Description

Computes three different summary statistics: (1) TotalArea total area of each polygon; (2) NoPoints number of multipoint objects within a given polygon; and, (3) Ratio ratio between NoPoints and TotalArea covered within a polygon.

Usage

point_calc(
  point_data,
  higher_geo_lay,
  unique_id_code,
  class_col,
  crs,
  total_points = TRUE
)

Arguments

point_data

multipoint object of class sf, sfc or sfg.

higher_geo_lay

multipolygon object of class sf, sfc or sfg.

unique_id_code

a string; indicating a unique ID column of higher_geo_lay, used as the summary areas.

class_col

a string; indicating a column name for point_data containing information on a target point classification. This is used when total_points = FALSE.

crs

coordinate reference system: integer with the EPSG code, or character based on proj4string.

total_points

logical; if the target is to measure the total number of points set to TRUE, by setting to FALSE, it returns the total number of points by class. If missing, it defaults to TRUE.

Details

The function requires two sets of data: a layer of geographic polygons, and a layer of points

If points have been categorised into classes, the function can return the same summary measures for each class if total_points = FALSE by specifying the column that contains the classification in class_col

Value

if total_points = TRUE: A tibble data frame objects containing four columns is returned:

the unique_id_code of higher_geo_lay
the total area of each polygon in higher_geo_lay (TotalArea)
the total number of point features point_data (NoPoints), and
the ratio between the total number of point features point_data and the the total area of higher_geo_lay polygon (Ratio).

if total_points = FALSE: A list of three tibble data frame objects is returned.

The object PointsLong contains three columns: the unique_id_code of higher_geo_lay, the class_col of point_data, the number of point features point_data by class (NoPoints), the total area of each polygon in higher_geo_lay (TotalArea) and the ratio between the number of point features by class point_data and the the total area of higher_geo_lay polygon (Ratio).
The object PointsCountWide: Returns the point counts of PointsLong by unique_id_code and class_col in a wide format.
The object PointsRatioWide: Returns the ratio of PointsLong by unique_id_code and class_col in a wide format.

Examples

## Run point_calc() using the packages' dummy data sets.
## The data sets are georeferenced on wgs84. However, a planar system is used to measure areas.
## For the examples provided here, points and polygons relate to the United Kingdom.
## So the British National Grid is used.

## Not run:
## This example returns the total points count and ratio
# outcome1 <- point_calc(
# point_data = points,
# higher_geo_lay = pol_large,
# unique_id_code = "large_pol_",
# crs = "epsg:27700",
# total_points = TRUE)



## This example returns the points count and ratio by class
# outcome2 <- point_calc(
# point_data = points,
# higher_geo_lay = pol_large,
# unique_id_code = "large_pol_",
# class_col = "class_name",
# crs = "epsg:27700",
# total_points = FALSE)
## End(Not run)

Point geospatial layer.

Description

Toy dataset of point data.

Usage

points

Format

A geospatial file of ten points georeferenced in wgs84.

Source

Own dataset.

Large polygons geospatial layer.

Description

Toy dataset of polygon data.

Usage

pol_large

Format

A geospatial file of three polygons georeferenced in wgs84.

Source

Own dataset.

Small polygons geospatial layer.

Description

Toy dataset of polygon data.

Usage

pol_small

Format

A geospatial file of eight polygons georeferenced in wgs84.

Source

Own dataset.