Let it snow!

December 14, 2012

(This article was first published on Probability and statistics blog » r, and kindly contributed to R-bloggers)

A couple days ago I noticed a fun piece of R code by Allan Roberts, which lets you create a digital snowflake by cutting out virtual triangles. Go give it a try. Roberts inspired me to create a whole night sky of snowflakes. I tried to make the snowfall look as organic as possible. There are lots of options to adjust. Here’s the code, have fun and Happy Holidays!

# Code by Matt Asher for statisticsblog.com
# Feel free to modify and redistribute 
 
# How many flakes do you want to fall?
flakes = 100
 
# Width and height of your space
width = 800
height = 600
 
# Initial wind
wind = 0
 
# Setup the background of the plot and margins
par(bg = "black")
par(oma=c(0,0,0,0))
par(mar=c(0,0,0,0))
plot(0, 0, col="black", pch=".", xlim=c(0,width), ylim=c(0,height), axes=F)
 
for(i in 1:flakes) {
    startY = height
    startX = runif(1,1,width)
 
    xPos = startX
    yPos = startY
 
    for(j in 1:height) {
 
		# Optional drift in wind
		wind = wind + rcauchy(1,0,.05)
 
		# Update snowflake position
        xPos = xPos + rnorm(1,.1,1.5)
        yPos = yPos - runif(1,4,20)
 
        # Are we in the space, if so display it
        if(xPos &gt; 0 &amp;&amp; xPos &lt;= width &amp;&amp; yPos &gt; 0 &amp;&amp; yPos &lt;= height) {
            points(round(xPos), round(yPos), col="white", pch=8)
 
            # System dely, slows down the flakes
            Sys.sleep(0.1)
        }
    }
}