calc_sdd {aspace}

Calculate the Standard Distance Deviation (Standard Distance)

Description

This function computes the Standard Distance Deviation (SDD) or Standard Distance from a set of points.

Usage

calc_sdd(id=1, centre.xy=NULL, calccentre=TRUE, weighted=FALSE,
 weights=NULL, points=NULL, verbose=FALSE)

Arguments

id

A unique integer to identify a SDD estimate

centre.xy

A vector of length 2, containing the x- and y-coordinates of the SDD centre

calccentre

Boolean: Set to TRUE if the mean center is to be calculated

weighted

Boolean: Set to TRUE if the weighted mean center is to be computed with weighted coordinates

weights

Weights applied to point observations, number of weights should equal the number of observations

points

A 2-column matrix or data frame containing the set of point observations input to the calc_sdd function

verbose

Boolean: Set to TRUE if extensive feedback is desired on the standard output

Details

Use the LOCATIONS element in the output list object along with the ATTRIBUTES elements can be used to produce shapefiles or other vector point files for geographic data.

Value

The returned result is a list:

TYPE

The type of calculation results stored in the object: BOX, SDD, SDE, CMD, CF, or CF2PTS, MNC, MDC

DATE

The date and time that the function was run

ID

Identifier for the SDD shape - it should be unique

LOCATIONS

Locations pertinent for the SDD that can be used with ATTRIBUTES if wishing to build a vector point file for geographic data outside of this pacakge.

FORPLOTTING

Coordinates and identifiers used for plotting by plot_sdd()

ATTRIBUTES

Attributes for the output SDD that can be used with LOCATIONS coordinates if wishing to build a vector point file for geographic data outside of this package.

id

Identifier for the SDD shape - it should be unique

calccentre

Boolean: TRUE if mean centre is computed

weighted

Boolean: TRUE if the weighted mean centre is to be used instead

CENTRE.x

X-coordinate of the centre

CENTRE.y

Y-coordinate of the centre

SDD.radius

SDD value, radius of the SDD

SDD.area

Area of the SDD circle

Note

Results specific for plotting are stored in the FORPLOTTING element within the produced list object. Pass the entire object to plot_sdd() and the function automatically extracts this information. This function can be used on its own (once) or repetitively in a loop to process grouped point data stored in a larger table. When used repetitively, be sure to increment the id argument to ensure that each SDD has a unique identifier.

Author(s)

Tarmo K. Remmel, Randy Bui, Ron Buliung

See Also

calc_box, calc_sde, calc_cmd, calc_cf, calc_cf2pts, calc_mnc, calc_mdc

Examples

# SDD EXAMPLE
data(activities)
a <- calc_sdd(id=1, centre.xy=NULL, calccentre=TRUE, points=activities)
str(a)
print(a)

# IF THE RESULT OF THIS FUNCTION IS STORED TO AN OBJECT, THE plot_box()
# FUNCTION WILL TAKE THAT OBJECT AS INPUT FOR PLOTTING VIA THE datin ARGUMENT

# SDD TO SHAPEFILE EXAMPLE (REMOVE THE COMMENTS TO RUN)
# shp <- convert.to.shapefile(a$LOCATIONS, a$ATTRIBUTES,"id",5)
# write.shapefile(shp, "SDD_Shape", arcgis=T)