I have a two-dimensional numpy array and I am wondering how I can create a new two-dimensional numpy array represent the ranking of the values based on all items in the original 2d array.
I would like to use the following array :
anArray = [[ 18.5, 25.9, 7.4, 11.1, 11.1]
[ 33.3, 37. , 14.8, 22.2, 25.9]
[ 29.6, 29.6, 11.1, 14.8, 11.1]
[ 25.9, 25.9, 14.8, 14.8, 11.1]
[ 29.6, 25.9, 14.8, 11.1, 7.4]]
to create a new rank ordered array [based on all values and having same rank for multiple numbers] :
anOrder = [[ 6, 4, 9, 8, 8]
[ 2, 1, 7, 5, 4]
[ 3, 3, 8, 7, 8]
[ 4, 4, 7, 7, 8]
[ 3, 4, 7, 8, 9]]
Thank you.
That's a routine work for np.unique with its optional argument return_inverse that tags each element based on the uniqueness among other elements, like so -
_,id = np.unique(anArray,return_inverse=True)
out = (id.max() - id + 1).reshape(anArray.shape)
Sample run -
In [17]: anArray
Out[17]:
array([[ 18.5, 25.9, 7.4, 11.1, 11.1],
[ 33.3, 37. , 14.8, 22.2, 25.9],
[ 29.6, 29.6, 11.1, 14.8, 11.1],
[ 25.9, 25.9, 14.8, 14.8, 11.1],
[ 29.6, 25.9, 14.8, 11.1, 7.4]])
In [18]: _,id = np.unique(anArray,return_inverse=True)
In [19]: (id.max() - id + 1).reshape(anArray.shape)
Out[19]:
array([[6, 4, 9, 8, 8],
[2, 1, 7, 5, 4],
[3, 3, 8, 7, 8],
[4, 4, 7, 7, 8],
[3, 4, 7, 8, 9]])