Smooth Layer

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Description

Plot a layer of smoothed data. It can also compute a ratio of potentials.

This function is a wrapper around the quickStewart function in SpatialPosition package.

The SpatialPosition package also provides:

  • vignettes to explain the computation of potentials;

  • more customizable inputs and outputs (custom distance matrix, raster output...);

  • other functions related to spatial interactions (Reilly and Huff catchment areas).

Usage

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smoothLayer(spdf, df, spdfid = NULL, dfid = NULL, var, var2 = NULL,
  typefct = "exponential", span, beta, resolution = NULL, mask = NULL,
  nclass = 8, breaks = NULL, col = NULL, border = "grey20", lwd = 1,
  legend.pos = "bottomleft", legend.title.txt = "Potential",
  legend.title.cex = 0.8, legend.values.cex = 0.6, legend.values.rnd = 0,
  legend.frame = FALSE, add = FALSE)

Arguments

spdf

a SpatialPolygonsDataFrame.

df

a data frame that contains the values to compute If df is missing spdf@data is used instead.

spdfid

name of the identifier field in spdf, default to the first column of the spdf data frame. (optional)

dfid

name of the identifier field in df, default to the first column of df. (optional)

var

name of the numeric field in df used to compute potentials.

var2

name of the numeric field in df used to compute potentials. This field is used for ratio computation (see Details).

typefct

character; spatial interaction function. Options are "pareto" (means power law) or "exponential". If "pareto" the interaction is defined as: (1 + alpha * mDistance) ^ (-beta). If "exponential" the interaction is defined as: exp(- alpha * mDistance ^ beta). The alpha parameter is computed from parameters given by the user (beta and span).

span

numeric; distance where the density of probability of the spatial interaction function equals 0.5.

beta

numeric; impedance factor for the spatial interaction function.

resolution

numeric; resolution of the output SpatialPointsDataFrame (in map units).

mask

SpatialPolygonsDataFrame; mask used to clip contours of potentials.

nclass

numeric; a targeted number of classes (default to 8). Not used if breaks is set.

breaks

numeric; a vector of values used to discretize the potentials.

col

a vector of colors. Note that if breaks is specified there must be one less colors specified than the number of break.

border

color of the polygons borders.

lwd

borders width.

legend.pos

position of the legend, one of "topleft", "top", "topright", "left", "right", "bottomleft", "bottom", "bottomright". If legend.pos is "n" then the legend is not plotted.

legend.title.txt

title of the legend.

legend.title.cex

size of the legend title.

legend.values.cex

size of the values in the legend.

legend.values.rnd

number of decimal places of the values in the legend.

legend.frame

whether to add a frame to the legend (TRUE) or not (FALSE).

add

whether to add the layer to an existing plot (TRUE) or not (FALSE).

Details

If var2 is provided the ratio between the potentials of var (numerator) and var2 (denominator) is computed.

Value

An invisible SpatialPolygonsDataFrame is returned (see quickStewart).

See Also

quickStewart, SpatialPosition, choroLayer

Examples

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## Not run: 
data("nuts2006")

# Potential of GDP
smoothLayer(spdf = nuts3.spdf, df = nuts3.df, 
            var = 'gdppps2008',
            span = 75000, beta = 2, 
            mask = nuts0.spdf, 
            legend.title.txt = "GDP", 
            legend.pos = "topright", legend.values.rnd = -2)  

# Potential of GDP per Capita
nuts3.df$gdppps2008 <- nuts3.df$gdppps2008 * 1000000
smoothLayer(spdf = nuts3.spdf, df = nuts3.df, 
            var = 'gdppps2008', var2 = 'pop2008',
            span = 75000, beta = 2, 
            mask = nuts0.spdf, 
            legend.title.txt = "GDP PER CAPITA", 
            legend.pos = "topright", legend.values.rnd = -2)  

## End(Not run)             

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