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ch_02_problems.py
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ch_02_problems.py
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# -*- coding: utf-8 -*-
"""
Chapter 2 - The Vector
Programming problems
Coding the Matrix
"""
from plotting import plot
L = [[2, 2], [3, 2], [1.75, 1], [2, 1], [2.25, 1], [2.5, 1], [2.75, 1], [3, 1], [3.25, 1]]
plot(L)
def add2(v, w):
return [v[0]+w[0], v[1]+w[1]]
w = [1, 2]
plot([add2(_, w) for _ in L], 5)
# quiz 2.5.3
def scalar_vector_mult(alpha, v):
return [alpha*v[i] for i in range(len(v))]
# task 2.5.4
alpha = -0.5
plot([[_[0]*alpha, _[1]*alpha] for _ in L])
plot([add2(scalar_vector_mult(i/100., [3, 2]), [0.5, 1]) for i in range(101)], 4)
# 2.6.9
def segment(pt1, pt2):
return [add2(scalar_vector_mult(i/100., pt1),
scalar_vector_mult(1-i/100., pt2)) for i in range(101)]
plot(segment([3.5, 3], [0.5, 1.0]))
class Vec:
def __init__(self, labels, function):
self.D = labels
self.f = function
v0 = Vec({'A', 'B', 'C'}, {'A': 1})
# quiz 2.7.1
def zero_vec(D):
f = {_: 0 for _ in D}
return Vec(D, f)
v1 = zero_vec({'a', 'b', 'c'})
def setitem(v, d, val):
v.f[d] = val
setitem(v0, 'B', 2)
def getitem(v, d):
if d in v.f:
return v.f[d]
else:
return 0
def scalar_mult(v, alpha):
return Vec(v.D, {a: alpha*b for a, b in v.f.items()})
scalar_mult(v0, 2).f
def add(u, v):
return Vec(u.D | v.D, {d: getitem(u, d) + getitem(v, d) for d in u.D | v.D})
v = Vec({'A', 'B', 'C'}, {'A': 1, 'B': 2})
u = Vec(v.D, {'A': 5, 'C': 10})
add(u, v).f
# quiz 2.7.5
def neg(v):
return Vec(v.D, {d: getitem(v, d) * -1 for d in v.D})
# quiz 2.9.4
def list_dot(u, v):
return sum([a*b for a, b in zip(u, v)])
# example 2.9.7
D = {'memory', 'radio', 'sensor', 'cpu'}
rate = Vec(D, {'memory': 0.06, 'radio': 0.1, 'sensor': 0.004, 'cpu': 0.0025})
duration = Vec(D, {'memory': 1.0, 'radio': 0.2, 'sensor': 0.5, 'cpu': 1.0})
list_dot(rate.f.values(), duration.f.values())
# quiz 2.9.13
haystack = [1, -1, 1, 1, 1, -1, 1, 1, 1]
needle = [1., -1., 1, 1., -1., 1.]
def dot_product_list(needle, haystack):
result = []
for i in range(len(haystack)-len(needle)+1):
result.append(list_dot(haystack[i:i+len(needle)], needle))
return result
dot_product_list(needle, haystack)
# quiz 2.10.1
from vec import Vec
#def list2vec(L):
# return Vec(set(range(len(L))), {i: L[i] for i in range(len(L))})
# 2.11.4
from vecutil import list2vec, zero_vec
def triangular_solve_n(rowlist, b):
D = rowlist[0].D
n = len(D)
assert D == set(range(n))
x = zero_vec(D)
for i in reversed(range(n)):
x[i] = (b[i] - rowlist[i] * x)/rowlist[i][i]
return x
D = {'a', 'b', 'c'}
rowlist = [Vec(D, {'a': 2, 'b': 3, 'c': -4}),
Vec(D, {'b': 1, 'c': 2}),
Vec(D, {'c': 5})]
b = Vec(D, {'a': 10, 'b': 3, 'c': 15})
triangular_solve_n(rowlist, b)
# 2.12 lab
with open('voting_record_dump109.txt') as f:
mylist = list(f)
# 2.12.1
def create_voting_dict(strlist):
x = [_.split() for _ in strlist]
return {_[0]: [int(a) for a in _[3:]] for _ in x}
voting_dict = create_voting_dict(mylist)
# 2.12.2
def policy_compare(sen_a, sen_b, voting_dict):
a = voting_dict[sen_a]
b = voting_dict[sen_b]
return sum([a[i]*b[i] for i in range(len(a))])
policy_compare('Reid', 'Obama', voting_dict)
# 2.12.3
def most_similar(sen, voting_dict):
max_sim = None
max_sen = None
for s in voting_dict:
if s == sen:
continue
sim = policy_compare(sen, s, voting_dict)
if not max_sim:
max_sim = sim
max_sen = [s]
if sim > max_sim:
max_sim = sim
max_sen = [s]
if sim == max_sim and s not in max_sen:
max_sen.append(s)
return (max_sen, max_sim)
most_similar('Chafee', voting_dict)
# 2.12.4
def least_similar(sen, voting_dict):
min_sim = None
min_sen = None
for s in voting_dict:
if s == sen:
continue
sim = policy_compare(sen, s, voting_dict)
if not min_sim:
min_sim = sim
min_sen = [s]
if sim < min_sim:
min_sim = sim
min_sen = [s]
if sim == min_sim and s not in min_sen:
min_sen.append(s)
return (min_sen, min_sim)
least_similar('Santorum', voting_dict)
# 2.12.6
policy_compare('Wyden', 'Smith', voting_dict)
# 2.12.7
def find_average_similarity(sen, sen_set, voting_dict):
rslt = []
for s in sen_set:
rslt.append(policy_compare(sen, s, voting_dict))
return sum(rslt)/len(rslt)
mylist2 = [_.split() for _ in mylist]
dems = [_[0] for _ in mylist2 if _[1]=='D']
repubs = [_[0] for _ in mylist2 if _[1]=='R']
find_average_similarity('Wyden', dems, voting_dict)
for sen in voting_dict:
max_sim = None
max_sen = None
sim = find_average_similarity(sen, dems, voting_dict)
if not max_sim:
max_sim = sim
max_sen = sen
if sim > max_sim:
max_sim = sim
max_sen = sen
print(max_sen, max_sim)
# 2.12.8
def find_average_record(sen_set, voting_dict):
sum_votes = None
for sen in sen_set:
if not sum_votes:
sum_votes = voting_dict[sen]
votes = voting_dict[sen]
sum_votes = [sum_votes[i] + votes[i] for i in range(len(votes))]
return [_ / len(votes) for _ in sum_votes]
avg_dem_rec = find_average_record(dems, voting_dict)
def policy_compare(sen_a, sen_b, voting_dict):
a = voting_dict[sen_a]
b = voting_dict[sen_b]
return sum([a[i]*b[i] for i in range(len(a))])
for sen in voting_dict:
max_sim = None
max_sen = None
sim = sum([voting_dict[sen][i]*avg_dem_rec[i] for i in range(len(avg_dem_rec))])
if not max_sim:
max_sim = sim
max_sen = sen
if sim > max_sim:
max_sim = sim
max_sen = sen
print(max_sen, max_sim)
# 2.12.6
min_sim = None
min_sens = None
for sen1 in voting_dict:
for sen2 in voting_dict:
if sen1 != sen2:
sim = policy_compare(sen1, sen2, voting_dict)
if not min_sim or sim < min_sim:
min_sim = sim
min_sens = (sen1, sen2)
print(min_sens, min_sim)