Gradient descent

grdesc.py

#gradient ascent test
def linear(theta0,theta1,x):
	return theta0+theta1*x

def cost(theta0,theta1,xm):
	L=0
	for i in xm:
		Z=0
		Z= linear(theta0,theta1,i[0])-i[1]
		Z*=Z
		L+=Z
	L *=(1.0/(2*len(xm)))
	return L
def dcost(theta0,theta1,xm):
	L=0
	for i in xm:
		Z=0
		Z= linear(theta0,theta1,i[0])-i[1]
		L+=Z
	L*= 1.0/(len(xm))
	return L
def dcost2(theta0,theta1,xm):
	L=0
	for i in xm:
		Z=0
		Z= linear(theta0,theta1,i[0])-i[1]
		L+=(Z*i[0])
	L*= 1.0/(len(xm))
	return L
def grd(xm,alpha=0,theta0=1,theta1=1):
	alpha=0.01
	while cost(theta0,theta1,xm) > 0.0000000000000001:
		theta0x=theta0-alpha*dcost(theta0,theta1,xm)
		theta1x=theta1-alpha*dcost2(theta0,theta1,xm)
		theta0,theta1=theta0x,theta1x
	return theta0,theta1

def quack(z):
	l=[]
	for i in xrange(20):
		q=[i]
		q.append(z(i))
		l.append(q)
	return l
# 0,2
q=[[0, 0], [1, 2], [2, 4], [3, 6], [4, 8], [5, 10], [6, 12], [7, 14], [8, 16], [9, 18], [10, 20], [11, 22], [12, 24], [13, 26], [14, 28], [15, 30], [16, 32], [17, 34], [18, 36], [19, 38]]
# 4,5
l=[[0, 4], [1, 9], [2, 14], [3, 19], [4, 24], [5, 29], [6, 34], [7, 39], [8, 44], [9, 49], [10, 54], [11, 59], [12, 64], [13, 69], [14, 74], [15, 79], [16, 84], [17, 89], [18, 94], [19, 99]]
# 20,-10
p=[[0, 20], [1, 10], [2, 0], [3, -10], [4, -20], [5, -30], [6, -40], [7, -50], [8, -60], [9, -70], [10, -80], [11, -90], [12, -100], [13, -110], [14, -120], [15, -130], [16, -140], [17, -150], [18, -160], [19, -170]]
# 300,25
m=[[0, 300], [1, 325], [2, 350], [3, 375], [4, 400], [5, 425], [6, 450], [7, 475], [8, 500], [9, 525], [10, 550], [11, 575], [12, 600], [13, 625], [14, 650], [15, 675], [16, 700], [17, 725], [18, 750], [19, 775]]