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import tensorflow as tf
import numpy as np
import matplotlib.pyplot as plttf.__version__#where操作查找元素位置
#输入的tensor是Tr… 本笔记记录tf.where进行元素位置查找scatter_nd用于指派元素到tensor的特定位置meshgrid用作绘图的相关操作。
import tensorflow as tf
import numpy as np
import matplotlib.pyplot as plttf.__version__#where操作查找元素位置
#输入的tensor是True,False组成的tensor
tensor tf.random.uniform([3,3], minval-12, maxval12, dtypetf.int32)
print(tensor.numpy())#获得大于0的值的mask
mask tensor 0
print(mask)
#方式1通过boolean_mask获得大于0的元素的值
print(tf.boolean_mask(tensor, mask):\n, tf.boolean_mask(tensor, mask).numpy())
#方式2先通过where查询到大于0的元素位置然后用gather_nd收集
indices tf.where(mask)
print(indices for the ones greater than 0:\n, indices.numpy())
print(tf.gather_nd(tensor, indices):\n, tf.gather_nd(tensor, indices))#where带条件选择元素
#where(cond, tensor1, tensor2)
#传入cond如果cond对应位置为True会收集tensor1对应位置的元素否则收集tensor2对应位置的元素
tensor1 tf.random.uniform([3,3], minval-12, maxval12, dtypetf.int32)
tensor2 tf.random.uniform([3,3], minval-12, maxval12, dtypetf.int32)
print(tensor1)
print(tensor2)cond tensor1 0
print(Condition:\n, cond)
print(where(cond, tensor1, tensor2):\n, tf.where(cond, tensor1, tensor2))#scatter_nd将元素放到对应位置其他值为0
#scatter_nd(indices, updates, shape)
#indices指定要更新到的位置
#updates指定更新的值
#shape表示tensor的形状#1维tensor的例子
indices tf.constant([[4], [3], [1], [9]])
updates tf.constant([6, 7, 8, 9])
shape tf.constant([10])print(tf.scatter_nd(indices, updates, shape):\n, tf.scatter_nd(indices, updates, shape))#多维tensor的scatrer_nd
# shape为5x4x4
#将值更新到大维度的0和2处实际对应一个4x4的tensor
indices tf.constant([[0], [2], [4]])
updates tf.constant([[[1, 1, 1, 1],[1, 1, 1, 1],[1, 1, 1, 1],[1, 1, 1, 1],],[[2, 2, 2, 2],[2, 2, 2, 2],[2, 2, 2, 2],[2, 2, 2, 2],],[[3, 3, 3, 3],[3, 3, 3, 3],[3, 3, 3, 3],[3, 3, 3, 3],]])
shape tf.constant([5,4,4])
print(tf.scatter_nd(indices, updates, shape):\n, tf.scatter_nd(indices, updates, shape))#meshgrid绘图
#1. 设置x和y的linspace
y tf.linspace(-2., 2, 5)
x tf.linspace(-2., 2, 5)#获得坐标点tensor
xPoints, yPoints tf.meshgrid(x, y)
print(X points:\n, xPoints)
print(Y points:\n, yPoints)
#通过tf.stack获得点的xy集合
points tf.stack([xPoints, yPoints], axis2)
print(Collection of XY points on plane:\n, points)#meshgrid实例,z sin(x) sin(y)
x tf.linspace(0., 2 * 3.14, 500)
y tf.linspace(0., 2 * 3.14, 500)
xPoints, yPoints tf.meshgrid(x, y)
points tf.stack([xPoints, yPoints], axis2)z tf.math.sin(points[..., 0]) tf.math.sin(points[..., 1])
#绘制z的值
plt.figure(z sin(x) sin(y))
plt.imshow(z, originlower, interpolationnone)
plt.colorbar()#绘制等高线
plt.figure(plot contour)
plt.contour(xPoints, yPoints, z)
plt.colorbar()
plt.show()运行结果
