[Numpy-discussion] Vector magnitude?

[Robert Dailey]

Hi,

I have two questions:

1) Is there any way in numpy to represent vectors? Currently I'm using
'array' for vectors.

2) Is there a way to calculate the magnitude (length) of a vector in numpy?

Thanks.
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Re: [Numpy-discussion] Vector magnitude?

[Robert Dailey]

Oh I think I get it.

You mean the built-in len() function? This isn't what I am looking for.
len() returns the number of components in the vector (e.g. whether it is a
2D, 3D, etc vector). I found that magnitude can be calculated using hypot()
in the math module that comes with python. However, this method only appears
to work with 2D vectors. And yes, by magnitude I mean euclidean norm:

sqrt( x*x + y*y ) = magnitude (length) of a vector

On 9/5/07, Robert Dailey [EMAIL PROTECTED] wrote:

 Thanks for your response.

 I was not able to find len() in the numpy documentation at the following
 link:
 http://www.scipy.org/doc/numpy_api_docs/namespace_index.html

 Perhaps I'm looking in the wrong location?

 On 9/5/07, Matthieu Brucher [EMAIL PROTECTED]  wrote:

 
 
  2007/9/5, Robert Dailey  [EMAIL PROTECTED]:
  
   Hi,
  
   I have two questions:
  
   1) Is there any way in numpy to represent vectors? Currently I'm using
   'array' for vectors.
 
 
 
  A vector is an array with one dimension, it's OK. You could use a matrix
  of dimension 1xn or nx1 as well.
 
 
  2) Is there a way to calculate the magnitude (length) of a vector in
   numpy?
 
 
  Yes, len(a)
 
  Matthieu
 
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[Numpy-discussion] How-to: Uniform vector scale

[Robert Dailey]

Hi,

I have a scalar value S. I want to perform the following math on vectors A
and B (both of type array):

A + B * S

By order of operations, B * S should be done first. This is a vector
multiplied by a real number and should be valid. However, the interpreter
outputs:
ValueError: shape mismatch: objects cannot be broadcast to a single
shape

I am not sure how I am supposed to multiply a vector with a scalar value.
For example:

array([5,2]) * 2 = [10,4]

The above should happen. However, I get the error message instead. Any
ideas? Thanks.
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