PlotImage_Fn: Plot density surface on a triangulated mesh
In James-Thorson/movement_tools: Tools for movement operators in GMRF models

1	PlotImage_Fn(Vec, breaks, Xset, Yset, DFexpand, ...)

`Vec`
`breaks`
`Xset`
`Yset`
`DFexpand`
`...`

##---- Should be DIRECTLY executable !! ----
##-- ==>  Define data, use random,
##--	or do  help(data=index)  for the standard data sets.

## The function is currently defined as
function (Vec, breaks, Xset, Yset, DFexpand, ...) 
{
    X = c(Xset[1] - mean(diff(Xset))/2, Xset + mean(diff(Xset))/2)
    Y = c(Yset[1] - mean(diff(Yset))/2, Yset + mean(diff(Yset))/2)
    Z = matrix(Breaks_Fn(Vec[DFexpand[, "r_loc"]], breaks = breaks), 
        ncol = length(Xset))
    image(z = Z, x = X, y = Y, breaks = 1:length(breaks), col = Col(length(breaks) - 
        1), ...)
  }