Rounding function rounds all column entries except for three

Question

Am using following function:

def round_half_away_from_zero(n, decimals=1):
    rounded_abs = round_half_up(abs(n), decimals)
    return math.copysign(rounded_abs, n)   

def round_half_up(n, decimals=1):
    multiplier = 10 ** decimals
    return math.floor(n*multiplier + 0.5) / multiplier

def round_half_down(n, decimals=1):
    multiplier = 10 ** decimals
    return math.ceil(n*multiplier - 0.5) / multiplier

df['temp'] = df3['temp'].apply(lambda x: round_half_away_from_zero(x))

he float then updates and the whole column except three entries act like the supposed to: for example:

63.5 = 63.5
58.355 = 58.4
88.878 = 88.9
48.75 = 48.8

Strangely enough, only three entries dont work and they are:

67.75 = 67.7
58.25 = 58.2
46.65 = 46.6

If i just do the function on the single value it works, but not in the series, for example:

round_half_away_from_zero(67.5) ,

it works and gives 67.8, 58.3 and 46.7 respectively.

Any ideas, Thanks

Maybe this? https://stackoverflow.com/questions/10825926/python-3-x-rounding-behavior — FObersteiner, Nov 08 '19 at 08:17

score 0 · Answer 1 · answered Nov 08 '19 at 08:22

Your code works - cannot replicate your error:

import pandas as pd
import math

def round_half_away_from_zero(n, decimals=1):
    rounded_abs = round_half_up(abs(n), decimals)
    return math.copysign(rounded_abs, n)   

def round_half_up(n, decimals=1):
    multiplier = 10 ** decimals
    return math.floor(n*multiplier + 0.5) / multiplier

df = pd.DataFrame( {"A": [63.5, 58.355, 88.878, 48.75] , 
                    "B": [67.75, 58.25, 46.65, 67.75] })


df['A_ok'] = df['A'].apply(lambda x: round_half_away_from_zero(x))
df['B_ok'] = df['B'].apply(lambda x: round_half_away_from_zero(x))

print(df)

Output:

# python 2.7
        A      B  A_ok  B_ok
0  63.500  67.75  63.5  67.8
1  58.355  58.25  58.4  58.3
2  88.878  46.65  88.9  46.7
3  48.750  67.75  48.8  67.8

# python 3.6
        A      B  A_ok  B_ok
0  63.500  67.75  63.5  67.8
1  58.355  58.25  58.4  58.3
2  88.878  46.65  88.9  46.7
3  48.750  67.75  48.8  67.8

Thank you@ Patrick Artner! Perhaps it is the excel calculations before hand. — Jienkles, Nov 08 '19 at 09:13
Hi back to this question, i found out that the three numbers i have problems with — Jienkles, Nov 14 '19 at 12:25

score 0 · Accepted Answer · answered Nov 14 '19 at 18:33

0

Hi back to this question, i found out that the three numbers i have problems with when multiply the decimals by 100, it rounded down - this was a floating point problem and i solved it by converting to decimal package before rounding off

answered Nov 14 '19 at 18:33

Jienkles

133
9

Rounding function rounds all column entries except for three

2 Answers2