CODEWITHSUNDEEP
pythonpandas
Lucas Dresl
Lucas Dresl

Reputation: 1170

Pandas .round() is not rounded as desired

I have the following id from a huge dataframe with a lot of ids, i pick this one in particular to show you what is the problem

                 id  year    anual_jobs     anual_wage
874180  20001150368  2010          10.5    1071.595917

after this i code

df.anual_jobs= df.anual_jobs.round()

i get this error but code runs anyways.

A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

See the caveats in the documentation: http://pandas.pydata.org/pandas-
docs/stable/indexing.html#indexing-view-versus-copy
self[name] = value

my result is:

                 id  year    anual_jobs     anual_wage
874180  20001150368  2010          10.0    1071.595917

when i want to round anual_jobs to 11.0 instead of 10.0

Upvotes: 2

Views: 2284

Answers (2)

Matthias Fripp
Matthias Fripp

Reputation: 18645

As @cᴏʟᴅsᴘᴇᴇᴅ pointed out, this is happening because numpy rounds half-values to the nearest even integer (see docs here and a more general discussion here), and pandas uses numpy for most of its numerical work. You can resolve this by rounding the "old-fashioned" way:

import numpy as np
df.anual_jobs = np.floor(df.anual_jobs + 0.5)

or

import pandas as pd
df.anual_jobs = pd.np.floor(df.anual_jobs + 0.5)

As @cᴏʟᴅsᴘᴇᴇᴅ pointed out you can also resolve the slice assignment warning by creating your dataframe as a free-standing frame instead of a view on an older dataframe, i.e., execute the following at some point before you assign values into the dataframe:

df = df.copy()

Upvotes: 6

SamuelNLP
SamuelNLP

Reputation: 4136

If what you want is because of the half-integer use decimal

from decimal import Decimal, ROUND_HALF_UP

print(Decimal(10.5).quantize(0, ROUND_HALF_UP))
print(Decimal(10.2).quantize(0, ROUND_HALF_UP))

>> 11
>> 10

Upvotes: 1

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