Python numpy二维矩阵乘法
我有三个numpy矩阵x,r和r。其值为:Python numpy二维矩阵乘法,python,numpy,Python,Numpy,我有三个numpy矩阵x,r和r。其值为: x = np.array([[4,2], [0,-1], [-2,5], [2,6]]) y = np.array([[1,7], [2,6], [5,2]]) r = np.array([[2,2,1], [2,3,1], [9,5,1],
x = np.array([[4,2],
[0,-1],
[-2,5],
[2,6]])
y = np.array([[1,7],
[2,6],
[5,2]])
r = np.array([[2,2,1],
[2,3,1],
[9,5,1],
[2,0,4]])
我要做的是:(很难用语言来描述,所以我用代码来表达我想做的事情)
最后的v是我需要的,v等于
[[[103. 38.]
[ 38. 216.]]
[[100. 46.]
[ 46. 184.]]
[[111. -54.]
[-54. 82.]]]
没有for循环,有什么优雅的或类似python的方法来实现这一点吗
谢谢这应该适合您:
A = x[np.newaxis,...]-y[:,np.newaxis,:] # equivalent to (x-y[k]) for all k
B = A.swapaxes(1,2) # equivalent to (x-y[k]).transpose() for all k
C = r.T[:,np.newaxis,:]*B # equivalent to r[:, k] * (x - y[k]).transpose()
D = C@A # equivalent to r[:, k] *(x - y[k]).transpose() @ (x - y[k])
或者以无法阅读的形式
((r.T[:,np.newaxis,:]*(x[np.newaxis,...]
-y[:,np.newaxis,:]).swapaxes(1,2))@
(x[np.newaxis,...]-y[:,np.newaxis,:]))
证明:
>>> (v==((r.T[:,np.newaxis,:]*(x[np.newaxis,...]
-y[:,np.newaxis,:]).swapaxes(1,2))@
(x[np.newaxis,...]-y[:,np.newaxis,:]))).all()
True
>>> (v==((r.T[:,np.newaxis,:]*(x[np.newaxis,...]
-y[:,np.newaxis,:]).swapaxes(1,2))@
(x[np.newaxis,...]-y[:,np.newaxis,:]))).all()
True