randomwalk.

# animation-2.r
# author: Bryce Mecum ([email protected])
#
# Animations in R Tutorial
# Part 2 of 6
#
# Extend part 1 by plotting a random (uniform) walk starting in the bottom
# right-hand corner and moving North and West.

library(maps)

xrange <- 180:240
yrange <- 45:70

ndays <- 30

jump_distance_x <- 1
jump_distance_y <- 1

positions <- data.frame(day = 1:ndays, x = c(225, rep(NA, ndays - 1)), y = c(50, rep(NA, ndays - 1)))
positions

for(i in 2:ndays)
{
  positions[i,"x"] <- positions[i - 1,"x"] + runif(1, -jump_distance_x, 0)
  positions[i,"y"] <- positions[i - 1,"y"] + runif(1, 0, jump_distance_y)
}

positions

map('world2', xlim = range(xrange), ylim = range(yrange))
map.axes()

points(y ~ x,
       data = positions, 
       cex = 1, 
       col = "red", 
       pch = 19)

lines(y ~ x, data = positions)