# this functions plots an m by m "chessboard" with squares that are of size n by n
# using the colors b and w for alternate squares
# if s=1 we save the figure otherwise we show it
def chessboard(m,n,b,w,s):
# start with an empty list to hold the plot
board = plot([])
# variables i and j index the squares of the board
# variables k and l give the coordinates of the bottom left corners of the squares
# if m=20 and n=25, k and l would be the points between 0 and 500 with coordinates divisible by 25
# what m and n do you use to get points between 0 and 500 with coordinates divisible by 25?
for i in range(m):
k = n*i
for j in range(m):
l = n*j
# now I plot the (i,j)th square
# this will illustrate how to very the color based on a test
# and to assemble them into a single plot
# in your project you would use points instead of polygons (and control the size)
# and your color depends on extinction rather than alternating
# a square b if (i+j) is even, w if it is odd
if ((i+j) % 2) == 0: # % computes integer remainders
c = b
else:
c = w
# first we make a list of the corners of the (i,j)th square
square = [[k,l], [k+n,l], [k+n,l+n], [k,l+n]]
# convert this to a plotted square with color and add to the board
board += polygon(square, color=c)
# draw the board with same x and y scale (aspect_ratio) and mn dots to the inch (dpi) to scale a bit
if s:
board.save("board_"+ str(m)+"_"+str(n)+".pdf", aspect_ratio=1, axes=false, dpi=m*n)
else:
board.show(axes=false, aspect_ratio=1, dpi=m*n)
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# show a standard board
chessboard(8,10, "black", "lightgray", 0)
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# show and save a nonstandard board: click on the file name to open the pdf
chessboard(30,2, "red", "blue", 0)
chessboard(30,2, "red", "blue", 1)
# saving lets you get a larger scale view of the plot than you see in the notebook
# this example shows why you might want this : warning it takes a bit of time to run
chessboard(100, 5, "yellow", "green", 0)
chessboard(100, 5, "yellow", "green", 1)
