| Title: | Display Air Quality Model Output and Monitoring Data |
|---|---|
| Description: | Display air quality model output and monitoring data using scatterplots, grids, and legends. |
| Authors: | Jenise Swall [aut, cre], Kristen Foley [ctb] |
| Maintainer: | Jenise Swall <[email protected]> |
| License: | Unlimited |
| Version: | 0.9 |
| Built: | 2025-02-19 05:14:23 UTC |
| Source: | https://github.com/cran/aqfig |
This package contains several functions to help users draw figures to display air pollution measurements and air quality model output. These include functions to place a color legend to the right of a plot, to draw a scatterplot with the points' colors or sizes reflecting the value of a response variable, etc.
This function sets up a color palette with n colors,
with gradually changing hues of grey, purple, blue, green, yellow,
orange, red, and brown (in this order). This palette is a
particularly good choice for scatterplot.density
function, for which it is the default choice.
kristen.colors(n=64)kristen.colors(n=64)
n |
Number of colors to include in palette. |
This function calls colorRampPalette and returns
n colors from this palette.
Returns n colors (in hexadecimal).
This function is called by default by the function
scatterplot.density, which is included in this
package.
Original code was authored by Kristen Foley and included in the
precursor to scatterplot.density. Packaged into a new
function by Jenise Swall.
This data set gives the daily maximum ozone concentrations (in ppb) observed at a subset of 23 Clean Air Status and Trends Network (CASTNET) monitoring sites on August 9, 2004.
ozone1ozone1
A file in CSV format containing 23 records.
Hourly ozone data at CASTNET sites can be obtained from EPA's Clean Air Status and Trends Network program at http://www.epa.gov/castnet. Thanks to Steven Howard for his help collating and summarizing these hourly data.
This data set gives the daily maximum ozone concentrations (in ppb) observed at a subset of 23 Clean Air Status and Trends Network (CASTNET) monitoring sites on August 10, 2004.
ozone2ozone2
A file in CSV format containing 23 records.
Hourly ozone data at CASTNET sites can be obtained from EPA's Clean Air Status and Trends Network program at http://www.epa.gov/castnet. Thanks to Steven Howard for his help collating and summarizing these hourly data.
Given a list of points' coordinates and the values
observed at those points, return a scatterplot with points located
as specified by the coordinates and coded by color and/or size to
represnt the observed value at the location. This code is basically
a wrapper for a call to the function points.geodata in
the geoR package.
plot3d.points(x, y, z, zlim = range(z, na.rm = TRUE), add = FALSE, col = heat.colors(12), xlab, ylab, pch = 21, cex.min = 1, cex.max = 1, symbol.border.col = "black", plt.beyond.zlim = FALSE, ...)plot3d.points(x, y, z, zlim = range(z, na.rm = TRUE), add = FALSE, col = heat.colors(12), xlab, ylab, pch = 21, cex.min = 1, cex.max = 1, symbol.border.col = "black", plt.beyond.zlim = FALSE, ...)
x |
x-coordinates of locations at which response values |
y |
y-coordinates of locations at which response values |
z |
Response values |
zlim |
Vector of minimum and maximum values of |
add |
If FALSE (default), the function will begin a new plot. If TRUE, adds scatterplot to a pre-existing plot. |
col |
Color range to use for the scatterplot, with the first
color assigned to zlim[1] and last color assigned to zlim[2].
Default is “heat.colors(12)”, as it is for |
xlab |
The label for the x-axis. If not specified by the user,
defaults to the expression the user named as parameter |
ylab |
The label for the y-axis. If not specified by the user,
defaults to the expression the user named as parameter |
pch |
The point symbol to use. Possible values are 21, 22, 23,
24, and 25. This is because |
cex.min |
Minimum amount to shrink/expand the point symbols. |
cex.max |
Maximum amount to shrink/expand the point symbols. |
Parameters cex.min and cex.max control the minimum
and maximum amounts to shrink/expland the points, based on the
value of z. By default, these are both set to one, which
makes all the points the same size. For more information, see
the help page for points.geodata.
symbol.border.col |
This controls the color of the border around the plotting symbol. By default, it is black. If a border is not desired, use ‘symbol.border.col=“transparent”’. |
plt.beyond.zlim |
IF TRUE, and if |
... |
Any other parameters the user adds will be passed to the
|
This function is a wrapper to the points.geodata
function in the geoR package.
A scatterplot with points at (x,y). These points
are colored according to the correspoinding value of z and
the colors specified in col. They are sized according to the
corresponding value of z and the minimum and maximum sizes
specified by cex.min and cex.max.
Jenise Swall
# Plot ozone at each location using colors from rainbow.colors # and differently-sized points. Add a legend using function # vertical.image.legend (included in this package). data(ozone1) col.rng <- rev(rainbow(n=10, start=0, end=4/6)) z.rng <- c(40, 90) plot3d.points(x=ozone1$longitude, y=ozone1$latitude, z=ozone1$daily.max, xlab="longitude", ylab="latitude", col=col.rng, zlim=z.rng, cex.min=0.5, cex.max=1.5) # To verify, label the points with their concentrations. text(ozone1$longitude, ozone1$latitude+0.15, ozone1$daily.max, cex=0.7) # If maps package is available, put on state lines. if (require("maps")) map("state", add=TRUE, col="lightgray") # Put on legend. vertical.image.legend(col=col.rng, zlim=z.rng) # Plot second day of ozone data. Note that day 2 experienced a smaller # range of concentrations, so we plot day 2 on same scale as day 1. data(ozone1) data(ozone2) z.rng <- c(40, 90) col.rng <- rev(rainbow(n=10, start=0, end=4/6)) plot3d.points(x=ozone2$longitude, y=ozone2$latitude, z=ozone2$daily.max, xlab="longitude", ylab="latitude", col=col.rng, zlim=z.rng, cex.min=0.5, cex.max=1.5) # To verify, label the points with their concentrations. text(ozone2$longitude, ozone2$latitude+0.15, ozone2$daily.max, cex=0.7) # If maps package is available, put on state lines. if (require("maps")) map("state", add=TRUE, col="lightgray") vertical.image.legend(col=col.rng, zlim=z.rng) # When some z value(s) is/are much lower/higher than the others, # the outlying value(s) may appear in color at the extent # of the range, with the remainder of the data clustered in one (or # just a few) color bin(s). x <- 1:9 y <- 1:9 z <- c(0, 47:53, 100) col.rng <- rev(rainbow(n=7, start=0, end=4/6)) plot3d.points(x, y, z, col=col.rng) text(x, y+0.2, z, cex=0.8) # In vain, you might try to "fix" this by setting zlim so that the # color range reflects the main portion of the z values. You may # assume that the outlying value(s) will show up in the extreme edges # of the color range, but what will actually happen is that the # outlying values won't be plotted. plot3d.points(x, y, z, col=col.rng, zlim=c(47, 53)) text(x, y+0.2, z, cex=0.8) # Instead, specify zlim to reflect the main porition of the z values, # and set plt.beyond.zlim=TRUE. Now, z values below zlim[1] will be # plotted in the same color as zlim[1]; those above zlim[2] will be # plotted like z values of zlim[2]. But, remember, now there are # outlying values whose maginitudes cannot be easily ascertained! plot3d.points(x, y, z, zlim=c(47, 53), col=col.rng, plt.beyond.zlim=TRUE) text(x, y+0.2, z, cex=0.8)# Plot ozone at each location using colors from rainbow.colors # and differently-sized points. Add a legend using function # vertical.image.legend (included in this package). data(ozone1) col.rng <- rev(rainbow(n=10, start=0, end=4/6)) z.rng <- c(40, 90) plot3d.points(x=ozone1$longitude, y=ozone1$latitude, z=ozone1$daily.max, xlab="longitude", ylab="latitude", col=col.rng, zlim=z.rng, cex.min=0.5, cex.max=1.5) # To verify, label the points with their concentrations. text(ozone1$longitude, ozone1$latitude+0.15, ozone1$daily.max, cex=0.7) # If maps package is available, put on state lines. if (require("maps")) map("state", add=TRUE, col="lightgray") # Put on legend. vertical.image.legend(col=col.rng, zlim=z.rng) # Plot second day of ozone data. Note that day 2 experienced a smaller # range of concentrations, so we plot day 2 on same scale as day 1. data(ozone1) data(ozone2) z.rng <- c(40, 90) col.rng <- rev(rainbow(n=10, start=0, end=4/6)) plot3d.points(x=ozone2$longitude, y=ozone2$latitude, z=ozone2$daily.max, xlab="longitude", ylab="latitude", col=col.rng, zlim=z.rng, cex.min=0.5, cex.max=1.5) # To verify, label the points with their concentrations. text(ozone2$longitude, ozone2$latitude+0.15, ozone2$daily.max, cex=0.7) # If maps package is available, put on state lines. if (require("maps")) map("state", add=TRUE, col="lightgray") vertical.image.legend(col=col.rng, zlim=z.rng) # When some z value(s) is/are much lower/higher than the others, # the outlying value(s) may appear in color at the extent # of the range, with the remainder of the data clustered in one (or # just a few) color bin(s). x <- 1:9 y <- 1:9 z <- c(0, 47:53, 100) col.rng <- rev(rainbow(n=7, start=0, end=4/6)) plot3d.points(x, y, z, col=col.rng) text(x, y+0.2, z, cex=0.8) # In vain, you might try to "fix" this by setting zlim so that the # color range reflects the main portion of the z values. You may # assume that the outlying value(s) will show up in the extreme edges # of the color range, but what will actually happen is that the # outlying values won't be plotted. plot3d.points(x, y, z, col=col.rng, zlim=c(47, 53)) text(x, y+0.2, z, cex=0.8) # Instead, specify zlim to reflect the main porition of the z values, # and set plt.beyond.zlim=TRUE. Now, z values below zlim[1] will be # plotted in the same color as zlim[1]; those above zlim[2] will be # plotted like z values of zlim[2]. But, remember, now there are # outlying values whose maginitudes cannot be easily ascertained! plot3d.points(x, y, z, zlim=c(47, 53), col=col.rng, plt.beyond.zlim=TRUE) text(x, y+0.2, z, cex=0.8)
This code produces an image plot in the case in which there
is not a known response value z for every possible combination
of x and y. This ragged image plot is a variant of an
image plot which is not complete across the entire rectangle of the
gridded area.
ragged.image(x, y, z, zlim = range(z, na.rm = TRUE), add = FALSE, col = heat.colors(12), xlab, ylab, plt.beyond.zlim = FALSE, ...)ragged.image(x, y, z, zlim = range(z, na.rm = TRUE), add = FALSE, col = heat.colors(12), xlab, ylab, plt.beyond.zlim = FALSE, ...)
x |
x-coordinates of grid cell centers at which response values
|
y |
y-coordinates of grid cell centers at which response values
|
z |
Response values recorded at the grid cell centers whose
coordinates are given by ( |
zlim |
Vector of minimum and maximum values of |
add |
If FALSE (default), the ragged image will begin a new plot. If TRUE, adds ragged image to a pre-existing plot. |
col |
Color range to use for the ragged image, with the first
color assigned to zlim[1] and last color assigned to zlim[2].
Default is "heat.colors(12)", as it is for |
xlab |
The label for the x-axis. If not specified by the user,
defaults to the expression the user named as parameter |
ylab |
The label for the y-axis. If not specified by the user,
defaults to the expression the user named as parameter |
plt.beyond.zlim |
IF TRUE, and if |
... |
Any additional parameters to be passed to the
|
This code produces a ragged image plot. This is in contrast to
the standard image function, which assumes that there is a
known response value z for every combination of the elements of
x and y, i.e. that there is a complete rectangular grid,
or image. A ragged image plot is a variant of the regular image plot
which is not complete across the entire rectangle. The user specifies
vectors x, y, and z, such that x and
y identify a portion of the grid. This function maps the vector
z onto a matrix of the type needed for the image
function, but has NA entries for combinations of x and y
that are not listed. The NA values are not plotted by
image, so a ragged image will appear.
A ragged image, i.e. a portion of an image for which we have
specified grid cell centers x and y.
This function is slow if x, y, and z are long
vectors.
Jenise Swall
# Build x, y, and z. x <- c(1, 2, 3, 1, 2, 3) y <- c(1, 1, 1, 2, 2, 2) z <- 1:6 z.mat <- matrix(c(1:6), ncol=2) col.rng <- terrain.colors(6) # Show complete matrix. image(x=unique(x), y=unique(y), z.mat, zlim=range(z), col=col.rng, xlab="x", ylab="y") # Plot only part of this as a ragged image. Set z range so that this # image will use colors consistent with the previous one. ragged.image(x=x[1:4], y=y[1:4], z=z[1:4], zlim=range(z), col=col.rng, xlab="x", ylab="y") # When some z value(s) is/are much lower/higher than the others, # the outlying value(s) may appear in color at the extent # of the range, with the remainder of the data clustered in one (or # just a few) color bin(s). x <- c(1, 2, 3, 1, 3, 2, 3, 1, 3) y <- c(4, 4, 4, 3, 3, 2, 2, 1, 1) z <- c(0, 47:53, 100) col.rng <- rev(rainbow(n=7, start=0, end=4/6)) ragged.image(x, y, z, col=col.rng) text(x, y, z, cex=0.8) # In vain, you might try to "fix" this by setting zlim so that the # color range reflects the main portion of the z values. You may # assume that the outlying value(s) will show up in the extreme edges # of the color range, but what will actually happen is that the # outlying values won't be plotted. ragged.image(x, y, z, col=col.rng, zlim=c(47, 53)) text(x, y, z, cex=0.8) # Instead, specify zlim to reflect the main porition of the z values, # and set plt.beyond.zlim=TRUE. Now, z values below zlim[1] will be # plotted in the same color as zlim[1]; those above zlim[2] will be # plotted like z values of zlim[2]. But, remember, now there are # outlying values whose maginitudes cannot be easily ascertained! ragged.image(x, y, z, zlim=c(47, 53), col=col.rng, plt.beyond.zlim=TRUE) text(x, y, z, cex=0.8)# Build x, y, and z. x <- c(1, 2, 3, 1, 2, 3) y <- c(1, 1, 1, 2, 2, 2) z <- 1:6 z.mat <- matrix(c(1:6), ncol=2) col.rng <- terrain.colors(6) # Show complete matrix. image(x=unique(x), y=unique(y), z.mat, zlim=range(z), col=col.rng, xlab="x", ylab="y") # Plot only part of this as a ragged image. Set z range so that this # image will use colors consistent with the previous one. ragged.image(x=x[1:4], y=y[1:4], z=z[1:4], zlim=range(z), col=col.rng, xlab="x", ylab="y") # When some z value(s) is/are much lower/higher than the others, # the outlying value(s) may appear in color at the extent # of the range, with the remainder of the data clustered in one (or # just a few) color bin(s). x <- c(1, 2, 3, 1, 3, 2, 3, 1, 3) y <- c(4, 4, 4, 3, 3, 2, 2, 1, 1) z <- c(0, 47:53, 100) col.rng <- rev(rainbow(n=7, start=0, end=4/6)) ragged.image(x, y, z, col=col.rng) text(x, y, z, cex=0.8) # In vain, you might try to "fix" this by setting zlim so that the # color range reflects the main portion of the z values. You may # assume that the outlying value(s) will show up in the extreme edges # of the color range, but what will actually happen is that the # outlying values won't be plotted. ragged.image(x, y, z, col=col.rng, zlim=c(47, 53)) text(x, y, z, cex=0.8) # Instead, specify zlim to reflect the main porition of the z values, # and set plt.beyond.zlim=TRUE. Now, z values below zlim[1] will be # plotted in the same color as zlim[1]; those above zlim[2] will be # plotted like z values of zlim[2]. But, remember, now there are # outlying values whose maginitudes cannot be easily ascertained! ragged.image(x, y, z, zlim=c(47, 53), col=col.rng, plt.beyond.zlim=TRUE) text(x, y, z, cex=0.8)
The plotting region of the scatterplot is divided into bins. The number of data points falling within each bin is summed and then plotted using the image function. This is particularly useful when there are so many points that each point cannot be distinctly identified.
scatterplot.density(x, y, zlim, xylim, num.bins=64, col=kristen.colors(32), xlab, ylab, main, density.in.percent=TRUE, col.regression.line=1, col.one.to.one.line=grey(0.4), col.bar.legend=TRUE, plt.beyond.zlim=FALSE, ...)scatterplot.density(x, y, zlim, xylim, num.bins=64, col=kristen.colors(32), xlab, ylab, main, density.in.percent=TRUE, col.regression.line=1, col.one.to.one.line=grey(0.4), col.bar.legend=TRUE, plt.beyond.zlim=FALSE, ...)
x |
Vector or matrix of x-coordinates of points to be plotted. Missing values are not permitted. |
y |
Vector or matrix of y-coordinates of points to be plotted. Missing values are not permitted. |
zlim |
Vector defining the minimum and maximum of the data
density values, to which to assign the two most extreme colors in the
|
xylim |
Specification of extreme values that the first and last
bins are expected to contain in the x- and y-directions. May be a
single vector of the limits for the x and y axes; e.g., using
‘xylim=c(0,120)’ specifies that, in both the x- and
y-directions, the first bin should contain 0 and the last contain
120. May also be a list in the form: ‘xylim=list(xlim=c(x1
,x2), ylim=c(y1, y2))’, allowing for the different ranges on the
axes. If not specified, xlim is the range of Note that |
num.bins |
Number of bins to be used when calculating the data density in both the x- and y-directions. May be a single number, e.g. ‘num.bins=50’, which produces 50 bins in each direction. May also be a list in the form ‘num.bins=list(num.bins.x=n1, num.bins.y=n2)’ to specify differing numbering of bins for the x- and y-directions. The default is to use 64 bins for both axes (‘num.bins=64’). Note that |
col |
Color range to use when drawing bins, with the first color assigned to ‘zlim[1]’ and last color assigned to ‘zlim[2]’. Default is ‘kristen.colors(32)’. |
xlab |
The label for the x-axis. If not specified by the user,
defaults to the expression the user named as parameter |
ylab |
The label for the y-axis. If not specified by the user,
defaults to the expression the user named as parameter |
main |
The main title for the density scatterplot. If not specified, the default is “Data Density Plot (%)” when ‘density.in.percent=TRUE’, and “Data Frequency Plot (counts)” otherwise. |
density.in.percent |
A logical indicating whether the density values should represent a percentage of the total number of data points, rather than a count value. Default is ‘density.in.percent=TRUE’. |
col.regression.line |
A color number or color name for the
regression line and estimated regression equation ( |
col.one.to.one.line |
A color number or color name for the regression one-to-one line to be overlaid on density scatterplot. If NULL, the one-to-one line is not displayed. Defaults to a dark grey line. If the one-to-one line is displayed, it will be as a dashed line (‘lty=3’). |
col.bar.legend |
A logical indicating whether a
“color legend” of the form given by
|
plt.beyond.zlim |
IF TRUE, and if |
... |
Any additional parameters to be passed to the
|
The plotting region of the scatterplot is divided into bins.
The number of data points falling within each bin is summed and then
plotted using the image function. The default is to
plot the percent of the data falling within each bin, rather than a
raw count value. The arguments xylim and num.bins can include
different settings for the x- and y-axis. This makes it easier to
plot different variables on each axis, e.g. temperature
vs. ozone. Note that xylim and num.bins together
determine how the bins are defined.
Note that xylim and num.bins together determine how the
bins are defined. This is done using the cut function.
Assigning values to bins is more complicated than might be expected.
For example, values that fall at cutoff points between bins are
difficult to deal with. This function accepts the default setting for
cut, which assigns values which fall on a cutoff point
to the bin on the left; that is, the intervals are open on the left
and closed on the right. This means that a point with x-value equal
to ‘xlim[1]’ and/or y-value equal to ‘ylim[1]’ would not be
assigned to any interval, which is probably not what the user intends
in this circumstance. Therefore, this code determines the number of
bins in the x-direction so that ‘xlim[1]’ and ‘xlim[2]’ are
at the center of the first and last bin in the x-direction (and
similarly for the y-direction). This means that the first and last
bins actually extend a bit past the limits specified. For most
applicatons, which use large numbers of data points and bins, this
shouldn't be noticeable, but it may be in smalled examples like the
first one given below.
A density scatterplot; that is, a pattern of shaded squares representing the counts/percentages of the points falling in each square.
Original version (plot.density.scatter.plot) by Kristen
Foley, adapted for aqfig by Jenise Swall
vertical.image.legend,
kristen.colors, image, cut
# As a simple test case, build x and y vectors consisting only of the # integers 1-3. x <- c( rep(1, 7), rep(2, 12), rep(3, 6) ) y <- c( rep(1, 5), rep(2, 2), rep(1, 2), rep(2, 8), rep(3, 2), rep(2, 2), rep(3, 4) ) # For this test case, I've totaled the counts below. count.df <- data.frame(x=rep(1:3, each=3), y=rep(1:3, times=3), ct=c(5, 2, 0, 2, 8, 2, 0, 2, 4) ) # Make a density scatterplot with counts. scatterplot.density(x, y, num.bins=3, col=heat.colors(7), density.in.percent=FALSE, col.one.to.one.line="green") text(count.df$x, count.df$y, count.df$ct, col="purple") # Make a density scatterplot with percentages. scatterplot.density(x, y, num.bins=3, col=heat.colors(7), col.one.to.one.line=1) text(count.df$x, count.df$y, count.df$ct/sum(count.df$ct)) # An example closer to actual usage. x <- rnorm(100000,50,5) y <- 3 + (.89*x) + rnorm(100000,0,5) scatterplot.density(x, y)# As a simple test case, build x and y vectors consisting only of the # integers 1-3. x <- c( rep(1, 7), rep(2, 12), rep(3, 6) ) y <- c( rep(1, 5), rep(2, 2), rep(1, 2), rep(2, 8), rep(3, 2), rep(2, 2), rep(3, 4) ) # For this test case, I've totaled the counts below. count.df <- data.frame(x=rep(1:3, each=3), y=rep(1:3, times=3), ct=c(5, 2, 0, 2, 8, 2, 0, 2, 4) ) # Make a density scatterplot with counts. scatterplot.density(x, y, num.bins=3, col=heat.colors(7), density.in.percent=FALSE, col.one.to.one.line="green") text(count.df$x, count.df$y, count.df$ct, col="purple") # Make a density scatterplot with percentages. scatterplot.density(x, y, num.bins=3, col=heat.colors(7), col.one.to.one.line=1) text(count.df$x, count.df$y, count.df$ct/sum(count.df$ct)) # An example closer to actual usage. x <- rnorm(100000,50,5) y <- 3 + (.89*x) + rnorm(100000,0,5) scatterplot.density(x, y)
Put color bar legend in the right-hand side margin of an existing plot.
vertical.image.legend(zlim, col)vertical.image.legend(zlim, col)
zlim |
Gives the range of z values to which the colors specified
in |
col |
Gives the range of colors to use. To keep multiple plots
consistent in terms of the colors assigned to various values, keep
|
This function works best when there is only one plot on the
device, in which case the margin space is straightforward (no
confusion between oma/omi and mar/mai,
etc. The user should finish making the main portion of the plot before adding
the legend; i.e., the user should add the legend last. This function
alters the par settings to draw the legend. Upon exit, it
resets them back to what they were before the function call.
Puts vertical color bar legend to the right of the plot.
Putting a legend on a plot is harder than it might seem. The user may
have to experiment with this function a bit to get it to work well for a
specific application. The user may also want to try the
imagePlot function in the fields package.
Jenise Swall
# Plot ozone at each location using colors from rainbow.colors # and differently-sized points. Add a legend using function # vertical.image.legend (included in this package). data(ozone1) col.rng <- rev(rainbow(n=10, start=0, end=4/6)) z.rng <- c(40, 90) plot3d.points(x=ozone1$longitude, y=ozone1$latitude, z=ozone1$daily.max, xlab="longitude", ylab="latitude", zlim=z.rng, col=col.rng, cex.min=0.5, cex.max=1.5) # To verify, label the points with their concentrations. text(ozone1$longitude, ozone1$latitude+0.15, ozone1$daily.max, cex=0.7) # If maps package is available, put on state lines. if (require("maps")) map("state", add=TRUE, col="lightgray") # Put on legend. vertical.image.legend(col=col.rng, zlim=z.rng)# Plot ozone at each location using colors from rainbow.colors # and differently-sized points. Add a legend using function # vertical.image.legend (included in this package). data(ozone1) col.rng <- rev(rainbow(n=10, start=0, end=4/6)) z.rng <- c(40, 90) plot3d.points(x=ozone1$longitude, y=ozone1$latitude, z=ozone1$daily.max, xlab="longitude", ylab="latitude", zlim=z.rng, col=col.rng, cex.min=0.5, cex.max=1.5) # To verify, label the points with their concentrations. text(ozone1$longitude, ozone1$latitude+0.15, ozone1$daily.max, cex=0.7) # If maps package is available, put on state lines. if (require("maps")) map("state", add=TRUE, col="lightgray") # Put on legend. vertical.image.legend(col=col.rng, zlim=z.rng)