Finding a cross /dot product of two vectors

[psbasha]

Hi,

Is there built in Math function is available to find the cross or dot product of two vectors?.



Thanks
PSB

[ghostdog74]

Hi,

Is there built in Math function is available to find the cross or dot product of two vectors?.



Thanks
PSB

you can use operator module
then you can sum then up after multiplying them together.
eg

>>> a = (1,2,3)
>>> b = (4,5,6)
>>> reduce( operator.add, map( operator.mul, a, b))
32
>>>                   
 

[bartonc]

Hi,

Is there built in Math function is available to find the cross or dot product of two vectors?.



Thanks
PSB

The NumPy package provide all the vector math that you will ever need. Also check out SciPy for all your advanced scientific computing needs.

[bvdet]

The NumPy package provide all the vector math that you will ever need. Also check out SciPy for all your advanced scientific computing needs.

Barton's suggestion is probably the way to go, but if you want to do your own, you may get what you need from this simple 3D vector class I wrote a few motths ago:

class Point(object):
    def __init__(self, x=0.0, y=0.0, z=0.0):
        self.x = float(x)
        self.y = float(y)
        self.z = float(z)
 
    def __str__(self):
        return '(%0.4f, %0.4f, %0.4f)' % (self.x, self.y, self.z)
 
    def __add__(self, other):
        return Point(self.x + other.x, self.y + other.y, self.z + other.z)
 
    def __sub__(self, other):
        return Point(self.x - other.x, self.y - other.y, self.z - other.z)
 
    def __mul__(self, f):
        return Point(self.x * f, self.y * f, self.z * f)
 
    def __repr__(self):
        return 'Point(%0.8f, %0.8f, %0.8f)' % (self.x, self.y, self.z)
 
    def dot_prod(self, other):
        return self.x*other.x + self.y*other.y + self.z*other.z
 
    def uv(self):
        return Point(self.x/self.magnitude(), self.y/self.magnitude(), self.z/self.magnitude())
 
    def cp(self, other):
        return Point(self.y*other.z - self.z*other.y, self.z*other.x - self.x*other.z, self.x*other.y - self.y*other.x)
 
    def magnitude(self):
        return (self.x**2 + self.y**2 + self.z**2)**0.5
 
p1 = Point(2.5, 3.5)
print "p1 =", p1
print "repr(p1) =", repr(p1)
print "eval(repr(p1)) =", eval(repr(p1))
p2 =  p1 + (Point(2.5, 3.5, 7.7))
print "p2 =", p2
p3 = p2 - p1
print "p3 =", p3
p4 = p2 * 6
print "p4 =", p4
d34 = p3.uv().dot_prod(p4.uv())
print "p3_uv dot p4_uv = d34 =", d34
print "p4 unit vector =", p4.uv()
print "p4 magnitude =", p4.magnitude()
print 'p3 cross product p4 =', p3.cp(p4)

>>> p1 = (2.5000, 3.5000, 0.0000)
repr(p1) = Point(2.50000000, 3.50000000, 0.00000000)
eval(repr(p1)) = (2.5000, 3.5000, 0.0000)
p2 = (5.0000, 7.0000, 7.7000)
p3 = (2.5000, 3.5000, 7.7000)
p4 = (30.0000, 42.0000, 46.2000)
p3_uv dot p4_uv = d34 = 0.94562842201
p4 unit vector = (0.4331, 0.6063, 0.6669)
p4 magnitude = 69.2707730576
p3 cross product p4 = (-161.7000, 115.5000, 0.0000)
>>>