Truncating decimal digits numpy array of floats

问题:

I want to truncate the float values within the numpy array, for .e.g.

2.34341232 --> 2.34 

I read the post truncate floating point but its for one float. I don't want to run a loop on the numpy array, it will be quite expensive. Is there any inbuilt method within numpy which can do this easily? I do need output as a float not string.

回答1:

Use numpy.round:

import numpy as np
a = np.arange(4) ** np.pi
a
=> array([  0.        ,   1.        ,   8.82497783,  31.5442807 ])
a.round(decimals=2)
=> array([  0.  ,   1.  ,   8.82,  31.54])

回答2:

Try out this modified version of numpy.trunc().

import numpy as np
def trunc(values, decs=0):
    return np.trunc(values*10**decs)/(10**decs)

Sadly, numpy.trunc function doesn't allow decimal truncation. Luckily, multiplying the argument and dividing it's result by a power of ten give the expected results.

vec = np.array([-4.79, -0.38, -0.001, 0.011, 0.4444, 2.34341232, 6.999])

trunc(vec, decs=2)

which returns:

>>> array([-4.79, -0.38, -0.  ,  0.01,  0.44,  2.34,  6.99])