On 4/9/07, Miquel Poch <[EMAIL PROTECTED]> wrote:
Hi,
I've got a function write in Matlab, and I need to tranlate it into
python. I've found an expresion like this:
?
BF = b0 + (b1 + (b2 + (b3 + (b4 + (b5 + b6*T).*T).*T).*T).*T).*T
or
dBFdT = b1 + (2 * b2 + (3 * b3 + (4 * b4 + (5 * b5 + 6*
b6*T).*T).*T).*T).*T
It's Horner's method for evaluating polynomials and their derivatives. You
can also do this in numpy as:
In [5]: p1,p2,p3,p4,p5,p6 = [1,2,3,4,5,6]
In [6]: p = poly1d([p6,p5,p4,p3,p2,p1])
In [7]: T = array([[1,2],[3,4]])
In [8]: p(T)
Out[8]:
array([[ 21, 321],
[2005, 7737]])
In [9]: polyder(p)(T)
Out[9]:
array([[ 70, 702],
[3098, 9178]])
Note the reversal of the coefficient order. Just make sure your arrays are
floats, the example I gave is all integers.
Chuck
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