How to round a numpy array

Question

I have a numpy array  something like below   data   np array    1 60130719e-01    9 93827160e-01    3 63108206e-04     and I want to round each element to two decimal places   How can I do so

User · Answer

It is worth noting that the accepted answer will round small floats down to zero.

>>> import numpy as np 
>>> arr = np.asarray([2.92290007e+00, -1.57376965e-03, 4.82011728e-08, 1.92896977e-12])
>>> print(arr)
[ 2.92290007e+00 -1.57376965e-03  4.82011728e-08  1.92896977e-12]
>>> np.round(arr, 2)
array([ 2.92, -0.  ,  0.  ,  0.  ])

You can use set_printoptions and a custom formatter to fix this and get a more numpy-esque printout with fewer decimal places:

>>> np.set_printoptions(formatter={'float': "{0:0.2e}".format})
>>> print(arr)
[2.92e+00 -1.57e-03 4.82e-08 1.93e-12]

This way, you get the full versatility of format and maintain the full precision of numpy's datatypes.

Also note that this only affects printing, not the actual precision of the stored values used for computation.

User · Answer

Numpy provides two identical methods to do this  Either use  np round data  2    or  np around data  2    as they are equivalent   See the documentation for more information     Examples    gt  gt  gt  import numpy as np  gt  gt  gt  a   np array  0 015  0 235  0 112    gt  gt  gt  np round a  2  array  0 02  0 24  0 11    gt  gt  gt  np around a  2  array  0 02  0 24  0 11    gt  gt  gt  np round a  1  array  0    0 2  0 1

User · Answer

If you want the output to be  array  1 6e-01  9 9e-01  3 6e-04     the problem is not really a missing feature of NumPy  but rather that this sort of rounding is not a standard thing to do  You can make your own rounding function which achieves this like so   def my round value  N       exponent   np ceil np log10 value       return 10  exponent np round value 10   -exponent   N    For a general solution handling 0 and negative values as well  you can do something like this   def my round value  N       value   np asarray value  copy       zero mask    value    0      value zero mask    1 0     sign mask    value  lt  0      value sign mask     -1     exponent   np ceil np log10 value       result   10  exponent np round value 10   -exponent   N      result sign mask     -1     result zero mask    0 0     return result

[python] How to round a numpy array?

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