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I have not posted a thing in a long time. Did not mean for that to happen. I've been getting a project off my back that I hope will pay off a little bit. It is certain now that I will have to get into web dev stuff.

Rose curves in matplotlib

I saw this and thought these would be neat to plot

http://en.wikipedia.org/wiki/Rose_(mathematics)

Specifically because this image

http://en.wikipedia.org/wiki/File:Rose-rhodonea-curve-7x9-chart.svg

Rose curves are just the polar equations of the sort

r = a * sin((n / d) * theta)

Where a (normally 1.0) determines length of petals, and n/d (normally d = 1) determine shape of petals as the equation is plotted across the domain of the sin call.

I thought it would be cool to write a python script that lets the user play with the numerator / denominator of the coefficient, and also the colors as hex triplets preceded by a hash mark, like #addfad or #00bd39 .

Here's all the code, blogger eats my indents so watch out folks

#!/usr/bin/python

import os, sys, getopt

from matplotlib.pyplot import show, plot, savefig, box, xticks, yticks

from numpy import arange, cos, sin, pi

import time

import optparse

def main():

parser = optparse.OptionParser("usage: %prog [options]")

parser.add_option("--color", dest = "color",

default = "#aaaaaa", type = "string",

help = "line color")

parser.add_option("--bgcolor", dest = "bgcolor",

default = "#444444", type = "string",

help = "background color, void if transparent")

parser.add_option("-t", dest = "trans",

action = "store_true",

help = "set transparent bg")

parser.add_option("-n", dest = "n",

default = 1, type = int,

help = "numerator of coefficient")

parser.add_option("-d", dest = "d",

default = 1, type = int,

help = "denominator of coefficient")

(options, args) = parser.parse_args()

color = options.color

bgcolor = options.bgcolor

trans = options.trans

n = options.n

d = options.d

mktime = time.time()

if not os.path.exists('roseout'):

os.mkdir('roseout')

outfile = 'roseout/' + str(n) + "_" + str(d) + "_" + str(mktime)

if n < 1:

n = 1

if d < 1:

d = 1

n = int(n)

d = int(d)

n = float(n)

d = float(d)

k = n / d

theta = arange(0.0, d * 2.0 * pi, 0.01)

r = sin(k * theta)

x = r * cos (theta)

y = r * sin (theta)

xticks([])

yticks([])

box(on=None)

plot(x, y, color = color)

savefig(outfile + ".png", format="png", transparent = trans, facecolor=bgcolor)

if __name__ == "__main__":

main()

You use it by saving it as 'rose' or whatever (chmod'ing it to 744 or anything that lets you execute it), changing to the directory and typing

./rose -n 9 -d 2 --color "#FFFFFF" --bgcolor "#000000"

changing the integers and hex triplets to your own preferences.

I had to manually convert polar coordinates to x,y using the plot() call, rather than pyplot's polar() call, because somehow polar() was only plotting part of my shape. I had some help from redditor 'desrosiers' with minor math stuff and my arange() calls.