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).
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).
Value
An invisible
SpatialPolygonsDataFrame is returned (see quickStewart
).
Details
If var2 is provided the ratio between the potentials of var (numerator)
and var2 (denominator) is computed.
See also
quickStewart, SpatialPosition, choroLayer
Examples
## 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)
## ---------------------------------------------