Code syntax in python with numpy

Question

can someone please tell me the difference between these following two notations, one is working, the other one isn't but they seem the same to me.

def GradientDescentCostTest():

    theta = numpy.array([0, 0, 0], numpy.float)
    features = numpy.array([[80, 20, 0], [65, 30, 1], [70, 23, 1]], numpy.float)
    values = numpy.array([20, 10, 14], numpy.float)    

    # This works and returns a value for cost:
    sumOfSquareErrors = numpy.square(numpy.dot(features, theta) - values).sum()
    cost = sumOfSquareErrors/(len(values)*2)

    # This doesn't work and returns value 0.0 for cost:
    cost = 1/(len(values)*2) * numpy.square(numpy.dot(features, theta) - values).sum()    

    return cost

print GradientDescentCostTest()

Thanks

sure can you provide enough to make your samples runnable (ie an example for all the undefined variables) — Joran Beasley
– Joran Beasley, Commented Feb 23, 2015 at 22:13

eddi · Accepted Answer · 2015-02-23 22:23:43Z

3

1/(len(values)*2) is equal to 0 because all operations are on integers. A simple fix is to instead use 1.0/(len(values)*2).

answered Feb 23, 2015 at 22:23

eddi

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