SUB-MATRIX extraction

[Pierre]

Hello,


let b = array([ [0,1,2] , [3,4,5] , [6,7,8] ])

How can I easily extract the submatrix [ [0 ,1], [3, 4]] ?

One possiblity is : b[[0,1],:][:,[0,1]] but it is not really easy !

Thanks.

 

[Jon Clements]

Hello,

let b = array([ [0,1,2] , [3,4,5] , [6,7,8] ])

How can I easily extract the submatrix [ [0 ,1], [3, 4]] ?

One possiblity is : b[[0,1],:][:,[0,1]] but it is not really easy !

Thanks.

x = numpy.array([ [0,1,2], [3,4,5], [6,7,8] ])
print x[0:2,:2]

array([[0, 1],

[3, 4]])

Check out http://www.scipy.org/Tentative_NumPy_Tutorial

hth,

Jon.

 

[Martin P. Hellwig]

Hello,

let b = array([ [0,1,2] , [3,4,5] , [6,7,8] ])

How can I easily extract the submatrix [ [0 ,1], [3, 4]] ?

One possiblity is : b[[0,1],:][:,[0,1]] but it is not really easy !

Thanks.

x = numpy.array([ [0,1,2], [3,4,5], [6,7,8] ])
print x[0:2,:2]

array([[0, 1],

[3, 4]])

Check out http://www.scipy.org/Tentative_NumPy_Tutorial

hth,

Jon.

Yeah numpy is great like that and is the most obvious and probably the
most right solution, however I'd like to mention if you are going to do
a lot of stuff that is going to look an awful lot like SQL, perhaps it
is easier to pump it in a (in :memory sqlite table and use it that
way. Chances are though that you are far better of with numpy.