quilt.plot {fields}R Documentation

Image plot for irregular spatial data.


Given a vector of z values associated with 2-d locations this function produces an image-like plot where the locations are discretized to a grid and the z values are coded as a color level from a color scale.


quilt.plot(x, y, z, nrow = 64, ncol = 64, grid = NULL, 


x A vector of the x coordinates of the locations -or- a a 2 column matrix of the x-y coordinates.
y A vector of the y coordinates -or- if the locations are passed in x the z vector
z Values of the variable to be plotted.
nrow Number of grid boxes in x.
ncol Number of grid boxes in y.
grid A grid in the form of a grid list.
... arguments to be passed to the image.plot function


This function combines the discretization to an image by the function as.image and is then graphed by image.plot. Locations that fall into the same grid box will have their z values averaged.

A similar function exists in the lattice package. The advantage of this fields version is that it uses the standard R graphics functions and is written in R code. Also, the aggregation to average values for z values in the same gird box allows for different choices of grids. If two locations are very close, separating them could results in very small boxes.

As always, legend placement is never completely automatic. Place the legend independently for more control, perhaps using image.plot in tandem with split.screen or enlarging the plot margin See help(image.plot) for examples of this function and these strategies.



See Also

as.image, image.plot, lattice, persp, drape.plot


data( ozone2)
# plot 16 day of ozone data set

quilt.plot( ozone2$lon.lat, ozone2$y[16,])
US( add=TRUE, col="grey", lwd=2)

# and ... if you are fussy 
# do it again 
# quilt.plot( ozone2$lon.lat, ozone2$y[16,],add=TRUE)
# to draw over the state boundaries. 

### adding a legend strip "by hand"
par( mar=c( 5,5,5,10)) # save some room for the legend
quilt.plot( ozone2$lon.lat, ozone2$y[16,], add.legend=FALSE)
image.plot(ozone2$lon.lat, ozone2$y[16,],legend.only=TRUE)


[Package fields version 3.3.1 Index]