from numpy import *
from matplotlib.pyplot import *
from mpl_toolkits.axes_grid.axislines import SubplotZero

def makeT(lim=1):	# Make the X-axis
	result = linspace(-lim,lim,100)
	return result

def sinc(x):		# define normlized sinc function
	return sin(pi*x)/(pi*x)
	
def raisedCos(x,B=0,T=1):	# define raised cosine function
	return sinc(x/T) * cos(pi*B*x/T) / (1 - (4*B*B*x*x/(T*T)) )
	
fig = figure(figsize=(8,4))
ax = SubplotZero(fig,111)
fig.add_subplot(ax)
ax.grid(True)
ax.set_xticks([-3,-2,-1,0,1,2,3])
ax.set_xticklabels(["-3T","-2T","-T","0","T","2T","3T"])
ax.set_ylim((-.3,1.2))
ax.set_yticklabels([])
for direction in ["xzero","yzero"]:
	ax.axis[direction].set_axisline_style("->")
	ax.axis[direction].set_visible(True)
for direction in ["left","right","bottom","top"]:
	ax.axis[direction].set_visible(False)

t = makeT(3.5)
ax.plot(t,raisedCos(t),label=r"$\beta=0$")
ax.plot(t,raisedCos(t,0.25),label=r"$\beta=0.25$")
ax.plot(t,raisedCos(t,0.5),label=r"$\beta=0.5$")
ax.plot(t,raisedCos(t,1.),label=r"$\beta=1$")

ax.text(3.5,0.,"t")
ax.text(0.1,1.1,"h(t)")
ax.legend()
#fig.show()
fig.savefig("Raised-cosine-impulse.svg",bbox_inches="tight",\
	pad_inches=.15)