python科学计算实验1

import numpy as np

arr = np.loadtxt("iris_sepal_length.csv", delimiter=",")
print(arr.sum())
print(arr.mean())
print(arr.std())
print(arr.var())
print(arr.min())
print(arr.max())
a, b = np.unique(arr, return_counts=True)

mask = np.lexsort((a,b))[::-1]
a = a[mask]
b = b[mask]
for c, d in zip(a, b):
    print(c, d)
print(len(b))

import numpy as np

arr1 = np.array([1, 2, 0, 0, 4, 0])
mask = arr1 != 0  # 布尔值索引
print(arr1[mask])
print("")

arr2 = np.random.random(9)
arr2.reshape((3, 3))
print(arr2.max())
print(arr2.min())
print("")

arr3 = np.random.random(9)
print(arr3.mean())
print("")

arr4 = np.arange(15)
arr4.resize(5, 3)
arr5 = np.arange(6)
arr5.resize(3, 2)
print(np.dot(arr4, arr5))
print("")

arr6 = np.arange(10)
arr6[(arr6 >= 3) & (arr6 <= 8)] *= -1
print(arr6)
print("")

arr7 = np.random.randint(0, 5, (5, 5))
print(arr7)
print("")

arr8 = np.linspace(0, 1, 12)
print(arr8)
print("")

arr9 = np.argsort(arr7[:, 2])  # argsort()用法，表示对数据进行从小到大进行排序，返回数据的索引值。
print(arr9)
print(arr7[arr9, :])
print("")

arr10 = np.random.randint(0, 9, (1, 5))
arr11 = np.random.randint(0, 9, (5, 1))
print(arr10 + arr11)