Column bind in Numpy 2 array and 1 matrix-CodePudding

I have two arrays:

dvec =  np.repeat(0, k);dvec
mu   = np.array([1,2,3,4,5])
Amat =  np.stack((dvec, mu), axis=1);

and a matrix

I = np.identity(k)

I want to column bind them in order to have one matrix

Amat =  np.stack((np.repeat(1,k), mu,I), axis=1);Amat

but when I do this python reports me

ValueError: all input arrays must have the same shape

How can I solve this error ?

CodePudding user response：

You can use numpy.column_stack: https://numpy.org/doc/stable/reference/generated/numpy.column_stack.html

k=5
dvec =  np.repeat(0, k);
mu   = np.array([1,2,3,4,5])
I = np.identity(k)

Amat=np.column_stack((dvec,mu,I))

Result:

array([[0., 1., 1., 0., 0., 0., 0.],
       [0., 2., 0., 1., 0., 0., 0.],
       [0., 3., 0., 0., 1., 0., 0.],
       [0., 4., 0., 0., 0., 1., 0.],
       [0., 5., 0., 0., 0., 0., 1.]])

CodePudding user response：

This will answer your question:

np.hstack((np.repeat(1, 5).reshape(-1,1), np.array([1,2,3,4,5]).reshape(-1,1), I))

np.stack joins a sequence of arrays along a new axis.
So it requires them to have the same shape.

What you need is hstack which stacks arrays in sequence horizontally (column bind)