import numpy as np
import pandas as pd
ar=np.arange(0,7)*5; ar
# array([ 0, 5, 10, 15, 20, 25, 30])
ar=np.arange(5) ** 4 ; ar
# array([ 0, 1, 16, 81, 256])
ar ** 0.5
# array([ 0., 1., 4., 9., 16.])
ar=3+np.arange(0, 30, 3); ar
# array([ 3, 6, 9, 12, 15, 18, 21, 24, 27, 30])
ar2=np.arange(1,11); ar2
# array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
print(ar)
print(ar2)
# [ 3 6 9 12 15 18 21 24 27 30]
# [ 1 2 3 4 5 6 7 8 9 10]
ar+ar2
# array([ 4, 8, 12, 16, 20, 24, 28, 32, 36, 40])
ar/ar2
# array([3., 3., 3., 3., 3., 3., 3., 3., 3., 3.])
ar**ar2
# array([ 3, 36, 729, 20736,
# 759375, 34012224, 1801088541, 110075314176,
# 7625597484987, 590490000000000])
ar=np.array([[1,1],[1,1]]); ar
# array([[1, 1],
# [1, 1]])
ar2=np.array([[2,2],[2,2]]); ar2
# array([[2, 2],
# [2, 2]])
ar*ar2
# array([[2, 2],
# [2, 2]])
ar.dot(ar2)
# array([[4, 4],
# [4, 4]])
ar=np.arange(1,5); ar
# array([1, 2, 3, 4])
ar2=np.arange(5,1,-1); ar2
# array([5, 4, 3, 2])
ar < ar2
# array([ True, True, False, False])
ar != ar2
# array([ True, True, False, True])
ar=np.arange(0,6); ar
# array([0, 1, 2, 3, 4, 5])
ar2=np.arange(0,8); ar2
# array([0, 1, 2, 3, 4, 5, 6, 7])
ar*ar2
# 長度不同，會發生錯誤
ar=np.array([[1,2,3],[4,5,6]]); ar
# array([[1, 2, 3],
# [4, 5, 6]])
ar.T
# array([[1, 4],
# [2, 5],
# [3, 6]])
np.transpose(ar)
# array([[1, 4],
# [2, 5],
# [3, 6]])
ar.reshape(6,)
# array([1, 2, 3, 4, 5, 6])
ar=np.arange(1,5); ar
# array([1, 2, 3, 4])
ar.prod()
# 24
ar.sum()
# 10
ar=np.array([np.arange(1,6),np.arange(1,6)]); ar
# array([[1, 2, 3, 4, 5],
# [1, 2, 3, 4, 5]])
#Columns
np.prod(ar,axis=0)
# array([ 1, 4, 9, 16, 25])
#Rows
np.prod(ar,axis=1)
# array([120, 120])
ar=np.array([[2,3,4],[5,6,7],[8,9,10]]); ar
# array([[ 2, 3, 4],
# [ 5, 6, 7],
# [ 8, 9, 10]])
ar.sum()
# 54
np.median(ar)
# 6.0
arr = np.random.randn(5, 4); arr
# array([[ 1.57393807, 0.34341465, 0.18690496, 0.87537642],
# [ 0.30326534, 0.95078482, -0.06609053, 0.57458184],
# [ 0.01752049, -0.9984003 , -0.32701152, 1.180956 ],
# [ 0.25866959, -0.54109039, 0.1545014 , -0.70679129],
# [-1.09377154, 0.63480085, 0.23812143, -0.84030038]])
rand = np.random.RandomState(42)
arr = rand.randn(5,4); arr
# array([[ 0.49671415, -0.1382643 , 0.64768854, 1.52302986],
# [-0.23415337, -0.23413696, 1.57921282, 0.76743473],
# [-0.46947439, 0.54256004, -0.46341769, -0.46572975],
# [ 0.24196227, -1.91328024, -1.72491783, -0.56228753],
# [-1.01283112, 0.31424733, -0.90802408, -1.4123037 ]])
arr.mean()
# -0.17129856144182892
arr.mean(axis=0)
# array([-0.19555649, -0.28577483, -0.17389165, -0.02997128])
arr.mean(axis=1)
# array([ 0.63229206, 0.4695893 , -0.21401545, -0.98963083, -0.75472789])