Drawing braces with Pyx

Question

How can I draw a “braced” line between two arbitrary points with Pyx?

It would look something like this:

Brace example http://tof.canardpc.com/view/d16770a8-0fc6-4e9d-b43c-a11eaa09304d

Answer 1

You can draw pretty braces using sigmoidals. I don't have Pyx installed so I'll just plot these using matplotlib (pylab here). Here beta controls the sharpness of the curves in the braces.

import numpy as nx
import pylab as px


def half_brace(x, beta):
    x0, x1 = x[0], x[-1]
    y = 1/(1.+nx.exp(-1*beta*(x-x0))) + 1/(1.+nx.exp(-1*beta*(x-x1)))
    return y

xmax, xstep = 20, .01
xaxis = nx.arange(0, xmax/2, xstep)
y0 = half_brace(xaxis, 10.)
y = nx.concatenate((y0, y0[::-1]))

px.plot(nx.arange(0, xmax, xstep), y)
px.show()

I plotted this along the x-axis to save screen space, but to get braces along the y-axis just swap x and y. Finally, Pyx has plenty of path drawing functionality built-in which coould also work for your needs.