Python: How do I create a new variable which is a boolean indicator of another variable's value?

Question

I have a dataset that looks like this:

DayDate   Value
19-01-01  500
19-01-02  750
19-01-03  1000

And I want to create this data:

DayDate Value  IsAboveMedian
19-01-01  500    False
19-01-02  750    False
19-01-03  1000   True

How do I do that in Python, add a Boolean that is a calculation of another variable?

hint: `df['Value'].median` gives you the median, and then you can use that to compare. — Quang Hoang, Sep 17 '19 at 15:15
Are you sure you want to do this? Anytime you add or delete a row, or update the `Value` of an existing row, the median will likely change. So now you have to go back and recalculate all the `IsAboveMedian` values. — John Gordon, Sep 17 '19 at 15:17

score 0 · Answer 1 · answered Sep 17 '19 at 15:15

0

You simply need:

df['IsAboveMedian'] = df['Value']>df['Value'].median()

Output:

DayDate Value  IsAboveMedian
19-01-01  500    False
19-01-02  750    False
19-01-03  1000   True

answered Sep 17 '19 at 15:15

harvpan

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Many thanks! I tried something similar but I failed, then I realized that the table I was working with had a multiindex. – cherrypie Sep 18 '19 at 08:24
This solution has nothing to do with index. Not sure what you are saying. – harvpan Sep 18 '19 at 14:15

score 0 · Answer 2 · answered Sep 17 '19 at 15:21

0

Hello this could help you. Check before posting question because this is already answered .

l = [2,58,8,69,9,7]
df  = pd.DataFrame(l, columns=['values'])
np.median(df['values'])

df["IsAboveMedian"] = df["values"].apply(lambda x: True if x>np.median(df['values']) else False)

answered Sep 17 '19 at 15:21

abdoulsn

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`True if x > np.median(...) else False` is redundant – rafaelc Sep 17 '19 at 15:29

Python: How do I create a new variable which is a boolean indicator of another variable's value?

2 Answers2