FField (version 0.1.0)

FFieldPtRep: Force field simulation for a set of points

Description

Force field simulation of interaction of set of points.

Usage

FFieldPtRep(coords,  rep.fact = 20,  rep.dist.lmt = 10,  attr.fact = 0.2,  adj.max = 0.1,  adj.lmt = 0.5, iter.max = 10000)

Arguments

coords

matrix or data.frame consisting of two columns (x and y coordinates).

rep.fact

repulsion force factor.

rep.dist.lmt

repulsion distance limit.

attr.fact

attraction force factor.

adj.max

maximum position adjustment at each iteration.

adj.lmt

position adjustment limit at which the simulation stops.

iter.max

the maximum number of iterations beyond which simulation will end and a warning will be reported.

Details

Points experience repulsion from one another and attraction to their original positions. Repulsion is inversely proportional to the square of the distance. Attraction is directly proportional to the distance. Very useful for placing text labels on graphs, such as scatterplots. Depending on the nature of the plot, parameters may need to be masaged for the simulation to converge. Assumes 1x1 coordinate aspect ratio and re-scaling of inputs may be needed. Default arguments are appropriate for adjusting 20-30 labels on a 100x100 area.

See Also

FField-package FFieldPtRepDemo

Examples

  library(ggplot2)
  
  # Normalize coordinates to maintain constant aspect ratio
  x.fact <- 100 / max(mtcars$wt)
  y.fact <- 100 / max(mtcars$mpg)
  
  # Repel points
  coords <-
    FFieldPtRep(coords = cbind(mtcars$wt * x.fact, 
                               mtcars$mpg * y.fact),
                rep.fact = 40)
  
  # Convert back to plot coordinates
  x.t <- coords$x / x.fact
  y.t <- coords$y / y.fact
  
  # Sample plot with repelled labels
  p2 <- 
    (ggplot(mtcars, aes(x = wt, 
                        y = mpg, 
                        label = rownames(mtcars)))  
     + geom_point()
     + geom_text(x = x.t,
                 y = y.t)
     + geom_segment(data = mtcars,
                    xend = x.t,
                    yend = y.t)
     + ggtitle("After"))
  p2