[Numpy-discussion] Matlab Translation - sqrt elementwise

Francesc Altet faltet@carabos....
Tue Apr 17 14:06:05 CDT 2007


El dt 17 de 04 del 2007 a les 20:58 +0200, en/na Miquel Poch va
escriure:
> Hi,
> 
> I've found the next expression write it in Matlab, 
> 
> Rtx   = sqrt(Rt);
> 
> Rtx is a matrix, and that's why I need sqrt() to operate elementwise.
> I've read NumPy tutorial, and I know it's possible, 
> 
> A set of this functions, has been provided wich optimize certain kinds
> of calculations on arrays. Most of this functions, such as sin, cos
> and sqrt are unary functions wich operate elementwise.  [Numerical
> Python, pg. 13]
> 
> but I don't know who to do it. The next error appear when I execute
> the code,
> 
> ''' exceptions.TypeError : only length-1 arrays can be converted to
> Python scalars ''

What are you doing? Operating element-wise is one of the most elementary
things that you can do with NumPy:

In [3]:a=numpy.array([[1,2],[3,4]])
In [4]:a
Out[4]:
array([[1, 2],
       [3, 4]])
In [5]:numpy.sqrt(a)
Out[5]:
array([[ 1.        ,  1.41421356],
       [ 1.73205081,  2.        ]])


Salut,

-- 
Francesc Altet    |  Be careful about using the following code --
Carabos Coop. V.  |  I've only proven that it works, 
www.carabos.com   |  I haven't tested it. -- Donald Knuth



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