ocean (version 0.1-0)

att.plot: Plot an attribute on an unstructured grid

Description

Given a vector of data, this function plots the data as a heatmap on an unstructured grid. The length of the data vector must be as long as either the number nodes in the grid or the number of elements in the grid. The grid is currently stored as a data.frame, but will be converted to an S4 object in the future.

Usage

att.plot(grid, att, col=heat.colors, add=F, zlim=NA, units='ll',
xlim=NA, ylim=NA, legend=F, border.col=NA, cex=1)

Arguments

grid

The grid to plot the attribute on. It must be a data.frame with grid$nodes$n, grid$nodes$x, grid$nodes$y, grid$elems$tri, andgrid$elems$n. grid$elems$tri is a

att

A vector to plot as a heatmap.

col

A function that takes a singel arguement n and returns n colors.

add

Should this plot be added to the current plot

zlim

Limits for the highest and lowest color intensity colors

units

Either 'll' for latitude and longitude or 'm' for meters

xlim

x limits for the plot

ylim

y limits for the plot

legend

Should a colorbar legend be added

border.col

Color of the polygon border colors

cex

Character expansion for cex and cex.*. See par.

Examples

## Construct points for a grid shaped like a bowl with a hole
np <- 16 # Number of points on each ring
nr <- 12 # Number of rings
theta <- seq(0, 2*pi, len=np+1)[seq(np)]
r <- sqrt(seq(0.01, 8, len=nr))
x <- rep(r, each=length(theta)) * rep(sin(theta), times=length(r))
y <- rep(r, each=length(theta)) * rep(cos(theta), times=length(r))
nn <- length(x)

## Assemble the points into a grid
tri <- matrix(0, 2 * np * (nr - 1), 3)
for(i in seq(nrow(tri))) {
    st.node <- ceiling(i / 2)
    if(i %% 2) {
        tri[i,] <- c(st.node, st.node + np + 1, st.node + 1)     
    } else {
        tri[i,] <- c(st.node, st.node + np, st.node + np + 1)
    }
    if(!(i %% (2 *np)))
        tri[i,3] <- st.node + 1 ## Next layer
    if(!((i + 1) %% (2 * np))) {
        tri[i,2] <- st.node + 1
        tri[i,3] <- st.node - np + 1
    }
}
ne <- nrow(tri)
grid <- list(nodes=list(x=x, y=y, lat=y, lon=x, n=nn),
             elems=list(tri=tri, n=ne))

## Plot the grid
att.plot(grid, -seq(ne), col=bathy.colors, units='m')