Package 'areal'

Asthma in St. Louis by Census Tract, 2017

Description

A simple features data set containing the geometry and asthma estimates from the Centers for Disease Control for St. Louis.

Usage

data(ar_stl_asthma)

Format

A data frame with 106 rows and 24 variables:

GEOID

full GEOID string

STATEFP

state FIPS code

COUNTYFP

county FIPS code

TRACTCE

tract FIPS code

NAMELSAD

tract name

ALAND

area of tract land, square meters

AWATER

area of tract water, square meters

ASTHMA

percent of residents with current asthma diagnosis, estimated

geometry

simple features geometry

Source

Centers for Disease Control's 500 Cities Data

Examples

str(ar_stl_asthma)
head(ar_stl_asthma)
summary(ar_stl_asthma$ASTHMA)

---

Race in St. Louis by Census Tract, 2017

Description

A simple features data set containing the geometry and associated attributes for the 2013-2017 American Community Survey estimates for race in St. Louis.

Usage

data(ar_stl_race)

Format

A data frame with 106 rows and 24 variables:

GEOID

full GEOID string

STATEFP

state FIPS code

COUNTYFP

county FIPS code

TRACTCE

tract FIPS code

NAMELSAD

tract name

ALAND

area of tract land, square meters

AWATER

area of tract water, square meters

TOTAL_E

total populaton count, estimated

TOTAL_M

total populaton count, margin of error

WHITE_E

white populaton count, estimated

WHITE_M

white populaton count, margin of error

BLACK_E

black populaton count, estimated

BLACK_M

black populaton count, margin of error

AIAN_E

american indian and alskan native populaton count, estimated

AIAN_M

american indian and alskan native populaton count, margin of error

ASIAN_E

asian populaton count, estimated

ASIAN_M

asian populaton count, margin of error

NHPI_E

native hawaiian and pacific islander populaton count, estimated

NHPI_M

native hawaiian and pacific islander populaton count, margin of error

OTHER_E

other race populaton count, estimated

OTHER_M

other race populaton count, margin of error

TWOPLUS_E

two or more races populaton count, estimated

TWOPLUS_M

two or more races populaton count, margin of error

geometry

simple features geometry

Source

tidycensus package

Examples

str(ar_stl_race)
head(ar_stl_race)
summary(ar_stl_race$ALAND)

---

Ward Boundaries in St. Louis, 2010

Description

A simple features data set containing the 2010 Ward boundaries, which are used as districts for Alderpersons who serve as elected representatives. The OBJECTID and AREA columns are included to simulate "real" data that may have superfluous or unclear columns.

Usage

data(ar_stl_wards)

Format

A data frame with 28 rows and 4 variables:

OBJECTID

Artifact from ESRI data creation

WARD

Ward number

AREA

area of each ward

geometry

simple features geometry

Source

City of St. Louis

Examples

str(ar_stl_wards)
head(ar_stl_wards)
summary(ar_stl_wards$AREA)

---

Clipped Ward Boundaries in St. Louis, 2010

Description

A simple features data set containing the 2010 Ward boundaries, which are used as districts for Alderpersons who serve as elected representatives. This version of the ward boundary has been modified so that the wards only extend to the Mississippi River shoreline.

Usage

data(ar_stl_wardsClipped)

Format

A data frame with 28 rows and 2 variables:

WARD

Ward number

geometry

simple features geometry

Source

City of St. Louis

Examples

str(ar_stl_wardsClipped)
head(ar_stl_wardsClipped)

---

Create Tessellations From SF Object

Description

Create Tessellations From SF Object

Usage

ar_tessellate(.data, shape = "square", size = 1)

Arguments

.data	An object of class sf to tessellate from
shape	One of 'square' or 'hexagon', the shape to make tessellations from
size	Numeric multiplier for size of tessellations, default is one kilometer

Value

A sf object

Examples

ar_tessellate(ar_stl_wards)

ar_tessellate(ar_stl_wards, shape = "hexagon", size = .75)

---

Validating Data for Interpolation

Description

ar_validate executes a series of logic tests for sf object status, shared coordinates between source and target data, appropriate project, and absence of variable name conflicts.

Usage

ar_validate(source, target, varList, method = "aw", verbose = FALSE)

Arguments

source	A sf object with data to be interpolated
target	A sf object that data should be interpolated to
varList	A vector of variable names to be added to the target object
method	The areal interpolation method validation is being performed for. This should be set to "aw". Additional functionality will be added as the package adds new interpolation techniques.
verbose	A logical scalar; if TRUE, a tibble with test results is returned

Value

If verbose is FALSE, a logical scalar is returned that is TRUE is all tests are passed and FALSE if one or more tests is failed. If verbose is TRUE, a tibble with detailed test results is returned.

See Also

c

Examples

ar_validate(source = ar_stl_asthma, target = ar_stl_wards, varList = "ASTHMA")

ar_validate(source = ar_stl_asthma, target = ar_stl_wards, varList = "ASTHMA", verbose = TRUE)

---

Aggregate Estimates Based on Target ID

Description

aw_aggregate sums the new estimates produced by aw_calculate based on the target id. These are then joined with the target data. This is the fourth step in the interpolation process after aw_weight.

Usage

aw_aggregate(.data, target, tid, interVar, newVar)

Arguments

.data	A given intersected dataset
target	A sf object that data should be interpolated to
tid	A unique identification number within target
interVar	A variable containing an interpolated value created by aw_calculate
newVar	Optional; a new field name to store the interpolated value in. If not specified, the interVar argument will be used as the new field name.

Value

A sf object with the interpolated value added to it.

Examples

library(dplyr)

race <- select(ar_stl_race, GEOID, TOTAL_E)
wards <- select(ar_stl_wards, WARD)

wards %>%
    aw_intersect(source = race, areaVar = "area") %>%
    aw_total(source = race, id = GEOID, areaVar = "area", totalVar = "totalArea",
             weight = "sum", type = "extensive") %>%
    aw_weight(areaVar = "area", totalVar = "totalArea", areaWeight = "areaWeight") %>%
    aw_calculate(value = "TOTAL_E", areaWeight = "areaWeight") -> intersect

aw_aggregate(intersect, target = wards, tid = WARD, interVar = TOTAL_E)

---

Calculate Estimated Population

Description

aw_calculate multiplies the given value by the area weight. This is the fourth step in the interpolation process after aw_weight.

Usage

aw_calculate(.data, value, areaWeight, newVar)

Arguments

.data	A given intersected dataset
value	A column within source to be interpolated
areaWeight	The name of the variable containing area weight per feature
newVar	Optional; a new field name to store the interpolated value in. If not specified, the value argument will be used as the new field name.

Value

An intersected file of class sf with a new field of interest recalculated with area weight

Examples

library(dplyr)

race <- select(ar_stl_race, GEOID, TOTAL_E)
wards <- select(ar_stl_wards, WARD)

wards %>%
    aw_intersect(source = race, areaVar = "area") %>%
    aw_total(source = race, id = GEOID, areaVar = "area", totalVar = "totalArea",
             weight = "sum", type = "extensive") %>%
    aw_weight(areaVar = "area", totalVar = "totalArea", areaWeight = "areaWeight") -> intersect

aw_calculate(intersect, value = "TOTAL_E", areaWeight = "areaWeight")

---

Interpolate Values

Description

This is the core function within the package for areal weighted interpolation. It validates both data sources before interpolating one or more listed values from the source data into the target data.

Usage

aw_interpolate(.data, tid, source, sid, weight = "sum", output = "sf", extensive,
    intensive)

Arguments

.data	A sf object that data should be interpolated to (this is referred to as the target elsewhere in the package).
tid	A unique identification number within target
source	A sf object with data to be interpolated
sid	A unique identification number within source
weight	For "extensive" interpolations, should be either "total" or "sum". For "intensive" interpolations, should be "sum". For mixed interpolations, this will only impact the calculation of the extensive variables.
output	One of either "sf" or "tibble"
extensive	A vector of quoted variable names to be treated as spatially extensive (e.g. population counts); optional if intensive is specified
intensive	A vector of quoted variable names to be treated as spatially intensive (e.g. population density); optional if extensive is specified

Details

Areal weighted interpolation can be used for generating demographic estimates for overlapping but incongruent polygon features. It assumes that individual members of a population are evenly dispersed within the source features (an assumption not likely to hold in the real world). It also functions best when data are in a projected coordinate system, like the UTM coordinate system.

Value

A sf object or a tibble with the value or values interpolated into the target data.

See Also

c

Examples

aw_interpolate(ar_stl_wards, tid = WARD, source = ar_stl_race, sid = GEOID, weight = "sum",
    output = "sf", extensive = "TOTAL_E")

aw_interpolate(ar_stl_wards, tid = WARD, source = ar_stl_asthma, sid = GEOID, weight = "sum",
    output = "tibble", intensive = "ASTHMA")

---

Intersect Source and Target Data

Description

aw_intersect intersects the source and target datasets and computes a new area field for the intersected data using the units associated with whatever project the data are currently in. This is the first step in the interpolation process after data validation and subsetting.

Usage

aw_intersect(.data, source, areaVar)

Arguments

.data	A sf object that data should be interpolated to
source	A sf object with data to be interpolated
areaVar	The name of the new area variable to be calculated.

Value

A sf object with the intersected data and new area field.

Examples

library(dplyr)

race <- select(ar_stl_race, GEOID, TOTAL_E)
wards <- select(ar_stl_wards, WARD)

aw_intersect(wards, source = race, areaVar = "area")

---

Preview Areal Weights

Description

Provides a preview of the weight options for areal weighted interpolation. This can be useful for selecting the final specification for aw_interpolate without having to construct a pipeline of all of the subfunctions manually.

Usage

aw_preview_weights(.data, tid, source, sid, type)

Arguments

.data	A sf object that data should be interpolated to (this is referred to as the target elsewhere in the package).
tid	A unique identification number within target
source	A sf object with data to be interpolated
sid	A unique identification number within source
type	One of either "extensive" (if the data are spatitally extensive e.g. population counts), "intensive" (if the data are spatially intensive e.g. population density), or "mixed" (if the data include both extensive and intensive values). If "extensive", the sum is returned for the interpolated value. If "intensive", the mean is returned for the interpolated value. If "mixed", vectors named "extensive" and "intensive" containing the relevant variable names should be specified in the dots.

Value

A tibble with the areal weights that would be used for interpolation if type is either "extensive" or "intensive". If it is mixed, two tibbles (one for "extensive" and one for "intensive") are returned as a list.

Examples

aw_preview_weights(ar_stl_wards, tid = WARD, source = ar_stl_race, sid = GEOID,
                   type = "extensive")

aw_preview_weights(ar_stl_wards, tid = WARD, source = ar_stl_asthma, sid = GEOID,
                   type = "intensive")

---

Calculate Total Area

Description

aw_total produces a new total area field that contains the total area by source id. This is the second step in the interpolation process after aw_intersect.

Usage

aw_total(.data, source, id, areaVar, totalVar, type, weight)

Arguments

.data	A sf object that has been intersected using aw_intersect
source	A sf object with data to be interpolated
id	A unique identification number
areaVar	The name of the variable measuring a feature's area, which is created as part of aw_intersect
totalVar	The name of a new total area field to be calculated
type	One of "intensive" or "extensive"
weight	One of "sum" or "total"

Value

A sf object with the intersected data and new total area field.

Examples

library(dplyr)

race <- select(ar_stl_race, GEOID, TOTAL_E)
wards <- select(ar_stl_wards, WARD)

wards %>%
    aw_intersect(source = race, areaVar = "area") -> intersect

aw_total(intersect, source = race, id = GEOID, areaVar = "area",
         totalVar = "totalArea", weight = "sum", type = "extensive")

---

Verify Correct Extensive-Sum Interpolation

Description

Verify Correct Extensive-Sum Interpolation

Usage

aw_verify(source, sourceValue, result, resultValue)

Arguments

source	A sf object with data to be interpolated
sourceValue	A column within source to be interpolated
result	A sf object with interpolated data
resultValue	A column within result with the interpolated values

Details

aw_verify ensures that the sum of the resulting interpolated value is equal to the sum of the original source value. This functionality only works for interpolations that are extensive and use the sum approach to calculating areal weights.

Value

A logical scalar; if TRUE, these two values are equal.

Examples

result <- aw_interpolate(ar_stl_wards, tid = WARD, source = ar_stl_race, sid = GEOID,
                         weight = "sum", output = "tibble", extensive = "TOTAL_E")

aw_verify(source = ar_stl_race, sourceValue = TOTAL_E, result = result, resultValue = TOTAL_E)

---

Calculate Areal Weight

Description

aw_weight creates an area weight field by dividing the area field by the total area field. This is the third step in the interpolation process after aw_weight.

Usage

aw_weight(.data, areaVar, totalVar, areaWeight)

Arguments

.data	A sf object that has been intersected using aw_intersect
areaVar	The name of the variable measuring a feature's area
totalVar	The name of the variable containing total area field by source id
areaWeight	The name of a new area weight field to be calculated

Value

A sf object with the intersected data and new area weight field.

Examples

library(dplyr)

race <- select(ar_stl_race, GEOID, TOTAL_E)
wards <- select(ar_stl_wards, WARD)

wards %>%
    aw_intersect(source = race, areaVar = "area") %>%
    aw_total(source = race, id = GEOID, areaVar = "area", totalVar = "totalArea",
             weight = "sum", type = "extensive") -> intersect

aw_weight(intersect, areaVar = "area", totalVar = "totalArea", areaWeight = "areaWeight")

---