Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

```# Escape Zombie Land!

# This is a simulation an escape from a hot zombie zone.  It freezes and gives an error if you get get killed so you had best not.  You attempt to navigate the zone by constructing waypoints.

# This is not a very clean set up and I would like to clean it up.  However, I have spent way more time on it than I intended.  So I might come back to it another day.

# Zombies are  distributed on a 10 x 10 grid.
gridxy = c(10,10)

# The number of zombies on the map
nzombies = 40

# How close a zombie needs to be to take out a human is defined here
same.space = .05

# This is how close a human needs to be to consider that the human has reached the waypoint.
waypoint.hit = .2

# I set up the zombie distribution randomly initially.
set.seed(1)
zombiexy = cbind(runif(nzombies)*gridxy, runif(nzombies)*gridxy)
plot(zombiexy, main="Zombies!", xlab="X", ylab="Y", col=grey(.2), xlim=c(0,gridxy), ylim=c(0,gridxy))

# Humans
startpoint = c(.5,.5)
humans = data.frame(x=c(0,-.25, .25), y=c(0,.25, -.25), name=c("You","Pete", "Jimmy"))

humansxy = humans[,1:2]

# Count humans
nhumans = nrow(humansxy)

(humansxy = humansxy+rep(startpoint, each=nhumans))

# Plot humans
points(humansxy, pch=8)

# Safety
safety = c(9.5,9.5)

# Waypoints, specify the waypoints the humans are to take to get to the destination.
waypoints = rbind(c(2.5,2), c(5,6), c(9.75, 7))

# Route
route = rbind(startpoint, waypoints, safety, safety, safety)
lines(route)

# A vector that will be shortenned as the simulation progresses
route.unreached = route

points(safety, safety, pch=7)

# Now let's imagine that each zombie has a sensory distance in which the zombie can detect humans.
detection.dist = 3

# How fast the zombies can move.  Zombies have no inertia.
zombie.acceleration = .075

# How fast humans can move
human.acceleration = .075

# Humans can outrun zombies by building up inertia
human.inertia = .6

# Initially everybody is at rest.
hmovement = zmovement = 0

# ---------------------------------------------------
#### Set up a single loop to check programming.

# First the zombies move

# First let's check how close each zombie is to each human.
# We will accomplish this by going through each zombie and checking how far away each zombie is from each human.
distances = matrix(NA, nrow=nzombies, ncol=nhumans)
for (i in 1:nzombies) for (ii in 1:nhumans) distances[i,ii] = (sum((zombiexy[i,]-humansxy[ii,])^2))^.5

target =  matrix(1:nrow(humansxy), ncol=nzombies, nrow=nrow(humansxy))[apply(distances, 1, order)[1,]]
# The apply command will apply the order command to each row while the [1,] selects only the critter that is closes.

plot(zombiexy, xlab = "X", ylab = "Y", main="If zombies did not have perception limitations")
for (i in 1:nzombies) arrows(x0=zombiexy[i,1], y0=zombiexy[i,2],
x1=humansxy[target,][i,1],
y1=humansxy[target,][i,2],
length=.1, col="red")
```
```  points(humansxy, pch=8)

# Safety
points(9.5,9.5, pch=7)

# However, if the target is outside of detection range then zombies cannot target that human.
target[distances[cbind(1:nzombies,target)]>detection.dist]=NA

# Plot the relationship between zombies and humans
plot(zombiexy, xlab = "X", ylab = "Y", main="Escape Zombie Land")
for (i in 1:nzombies) arrows(x0=zombiexy[i,1], y0=zombiexy[i,2],
x1=humansxy[target,][i,1],
y1=humansxy[target,][i,2],
length=.1, col="red")
# Plot humans
points(humansxy, pch=8)

# Safety
points(9.5,9.5, pch=7)

# This calculates the difference between the current position of each zombie and that of the closest human.
ab = zombiexy-humansxy[target,]

ab=ab[!is.na(target),]

# Now calculate the difference in the horizontal and vertical axes that the zombies will move as a projection into the direction of the closest zombie outside of the perceptive zone.
a.prime = zombie.acceleration/(1 + (ab[,2]^2)/(ab[,1]^2))^.5
b.prime = (zombie.acceleration^2-a.prime^2)^.5

# This corrects the movement to ensure that the zombies are moving at the humans rather than away from them.
zmovement = cbind(a.prime * sign(ab[,2]), b.prime * sign(ab[,1]))
between = function(xy1,xy2,point) ((point>xy1&pointxy2&point1) warntxt = paste(humans[humans.down,3], "are down!")

# Remove any "captured" humans
if (length(humans.down)>0) {
humansxy = humansxy[-humans.down,]
nhumans = nrow(humansxy)
}

# Now the surving humans get to move.

# However, we only calculate the movement for the leader (you) since all of the other humans move in parrellel to you.

# Movement is also much simpler since humans just run from one waypoint to the next.

# First we check if we have reached any waypoints (which we have since we start on one).
way.distance =
(sum((humansxy[1,]-route.unreached[1,])^2))^.5

if (way.distancexy1&pointxy2&point2) {

# First let's check how close each zombie is to each human.
# We will accomplish this by going through each zombie and checking how far away each zombie is from each human.
distances = matrix(NA, nrow=nzombies, ncol=nhumans)
for (i in 1:nzombies) for (ii in 1:nhumans) distances[i,ii] = (sum((zombiexy[i,]-humansxy[ii,])^2))^.5

if (nrow(humansxy)>1) target = matrix(1:nrow(humansxy), ncol=nzombies, nrow=nrow(humansxy))[apply(distances, 1, order)[1,]]
if (nrow(humansxy)==1) matrix(1, ncol=nzombies, nrow=1)
# The apply command will apply the order command to each row while the [1,] selects only the critter that is closes.

target[distances[cbind(1:nzombies,target)]>detection.dist]=NA

# Plot the relationship between zombies and humans
plot(0,0, type="n", xlab = "X", ylab = "Y", main="Escape Zombie Land", xlim=c(0,gridxy), ylim=c(0,gridxy))

# Safety
points(9.5,9.5, pch=7)

text(5,.25,warntxt)

# This calculates the difference between the current position of each zombie and that of the closest human.
ab = zombiexy-humansxy[target,]

ab=ab[!is.na(target),]

# Now calculate the difference in the horizontal and vertical axes that the zombies will move as a projection into the direction of the closest zombie outside of the perceptive zone.
a.prime = zombie.acceleration/(1 + (ab[,2]^2)/(ab[,1]^2))^.5
b.prime = (zombie.acceleration^2-a.prime^2)^.5

# This corrects the movement to ensure that the zombies are moving at the humans rather than away from them.
zmovement = cbind(a.prime * sign(ab[,2]), b.prime * sign(ab[,1]))
between = function(xy1,xy2,point) ((point>xy1&pointxy2&point1) warntxt = paste(humans[humans.down,3], "are down!")

# Remove any "captured" humans
if (length(humans.down)>0) {
humansxy = humansxy[-humans.down,]
nhumans = nrow(humansxy)
}

# Now the surving humans get to move.

# However, we only calculate the movement for the leader (you) since all of the other humans move in parrellel to you.

# Movement is also much simpler since humans just run from one waypoint to the next.

# First we check if we have reached any waypoints (which we have since we start on one).
way.distance = (sum((humansxy[1,]-route.unreached[1,])^2))^.5

if (way.distancexy1&pointxy2&point  # Let's see how we do at escaping zombie land
ani.options(ani.width=600, ani.height=600, interval=.25)
saveGIF(flocking( ani.pause=T), movie.name = "Zombies.gif", replace=T)

var vglnk = {key: '949efb41171ac6ec1bf7f206d57e90b8'};
(function(d, t) {
var s = d.createElement(t);
s.type = 'text/javascript';
s.async = true;
// s.defer = true;
var r = d.getElementsByTagName(t);
r.parentNode.insertBefore(s, r);
}(document, 'script'));

Related
ShareTweet