Numpy

Basic numpy:

import numpy as np

arr1 = np.array([0,1,2]) # 傳入 tuple 創建一維陣列
print(type(arr1))        # 列出 arr1 類別型態
print(arr1.shape)        # 列出 arr1 陣列大小
print(arr1.ndim)         # 列出 arr1 維度大小
print(arr1)              # 列出 arr1 內容
print(arr1[1])           # 找出arr1索引值為 1 的內容

arr2 = np.array([[0,1,2],
                 [4,5,6]]) # 傳入 tuple 創建二維陣列
print(type(arr2))          # 列出 arr2 類別型態
print(arr2.shape)          # 列出 arr2 陣列大小
print(arr2.ndim)           # 列出 arr2 維度大小
print(arr2)                # 列出 arr2 內容
print(arr2[1][1])          # 找出 arr2索引值為 1 的內容

reshape function in numpy

import numpy as np

arr1 = np.array([0,1,2,3,4,5,6,7,
                 8,9,10,11,12,13,14,15])
print(arr1.shape)

#reshape function
arr2 = arr1.reshape(2,8)  # 將維度改為 2x8
print(arr2)
print(arr2.shape)
arr3 = arr1.reshape(4,4)  # 將維度改為 4x4
print(arr3)
print(arr3.shape)

Numpy arrange: Generate a range of numbers in numpy

import numpy as np

# numpy.arange[start, stop)
x1 = np.arange(5)
print (x1)
print(x1.dtype)
x2 = np.arange(0,5,dtype = np.float32)
print (x2)
print (x2.dtype)
x3 = np.arange(0,10,2,dtype = np.float64)
print (x3)
print (x3.dtype)

Linspace

import numpy as np

# 從 1-10產生10個值
# linespace==> the inbetween from start and end
# endpoint = True can include the last sample

arr1 = np.linspace(1,10,10)
print(arr1)
# 從 1-10產生5個值
arr2 = np.linspace(1,10,5)
print(arr2)
# 從 1-1產生10個值
arr3 = np.linspace(1,1,10)
print(arr3)
# 從 1-10產生5個值,不包含10
arr4 = np.linspace(1, 10,  5, endpoint =  False)
print(arr4)

np.Logspace()

import numpy as np
# 默認底數是 10
#logspace

arr1 = np.logspace(1.0, 2.0,num=10) # ,num=10
#default logspace is 50
print (arr1)
# 底數為 2
arr2 = np.logspace(1,5,num=5,base=3)
print (arr2)