How can I floor a number to the nearest multiple of 0.2 in numpy?
For example, I have this:
0.2 * np.floor(xi / 0.2)
It works most of the time e.g.
>>> xi = 9.4
>>> 0.2 * np.floor(xi / 0.2)
9.4
However, it fails for some numbers, such as 9.6
>>> xi = 9.6
>>> 0.2 * np.floor(xi / 0.2)
9.4
I would expect the previous calculation to return 9.4.
How can I fix this?
This is because float format - note that 9.6/0.2 returns 47.9999999....
Some rounding here and there will do the trick:
round(0.2*np.floor(round(xi / 0.2,2)),1)
Inner rounding is 2 decimal places, to make sure you won't loose the precision, and still will have something to floor.
Outer round is - so you will have proper rounding to 0.2 (and not e.g. 9.6000...1)
Use np.round
0.2 * np.round(xi / 0.2)
output:
9.600000000000001
The little bit extra is due to floating point math.