def trimandshift(t, p):
	"""
	Takes the vectors given by the above function, 
	and chops out a day and samples at half hourly intervals.
	"""
	t3, p3 = [], [] 
	t2 = t[132+4*144:276+4*144]
	p2 = p[132+4*144:276+4*144]
	for i in range(len(t2)): 
		if (i%3) == 0: 
			t3.append(t2[i])
			p3.append(p2[i])
	return t3, p3