Replace negative values in an numpy array

Question

Is there a simple way of replacing all negative values in an array with 0  I m having a complete block on how to do it using a NumPy array  E g  a   array  1  2  3  -4  5    I need to return  1  2  3  0  5   a  lt  0 gives   False  False  False  True  False   This is where I m stuck - how to use this array to modify the original array

User · Accepted Answer

You are halfway there  Try   In  4   a a  lt  0    0  In  5   a Out 5   array  1  2  3  0  5

User · Answer

And yet another possibility   In  2   a   array  1  2  3  -4  5    In  3   where a lt 0  0  a  Out 3   array  1  2  3  0  5

User · Answer

Another minimalist Python solution without using numpy   0 if i  lt  0 else i for i in a   No need to define any extra functions  a    1  2  3  -4  -5 23  6   0 if i  lt  0 else i for i in a   yields   1  2  3  0  0  6

User · Answer

Try numpy clip    gt  gt  gt  import numpy  gt  gt  gt  a   numpy arange -10  10   gt  gt  gt  a array  -10   -9   -8   -7   -6   -5   -4   -3   -2   -1    0    1    2           3    4    5    6    7    8    9    gt  gt  gt  a clip 0  10  array  0  0  0  0  0  0  0  0  0  0  0  1  2  3  4  5  6  7  8  9     You can clip only the bottom half with clip 0      gt  gt  gt  a   numpy array  1  2  3  -4  5    gt  gt  gt  a clip 0  array  1  2  3  0  5     You can clip only the top half with clip max n    This is much better than my previous suggestion  which involved passing NaN to the first parameter and using out to coerce the type      gt  gt  gt  a clip max 2  array   1   2   2  -4   2     Another interesting approach is to use where    gt  gt  gt  numpy where a  lt   2  a  2  array   1   2   2  -4   2     Finally  consider aix s answer  I prefer clip for simple operations because it s self-documenting  but his answer is preferable for more complex operations

User · Answer

Here s a way to do it in Python without NumPy  Create a function that returns what you want and use a list comprehension  or the map function   gt  gt  gt  a    1  2  3  -4  5    gt  gt  gt  def zero if negative x         if x  lt  0          return 0       return x       gt  gt  gt   zero if negative x  for x in a   1  2  3  0  5    gt  gt  gt  map zero if negative  a   1  2  3  0  5

[python] Replace negative values in an numpy array

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