[SOLVED] Apply own function to every item in DataFrame

Issue

I have created a function to give out a rank based on the value in each cell of the table below:
Table name is "ranked"

Date        MMM     AOS     ABT
2016-01-31  55.0    411.0   102.0
2016-02-29  44.0    425.0   96.0
2016-03-31  29.0    410.0   70.0
2016-04-30  29.0    425.0   87.0
2016-05-31  46.0    409.0   52.0

Function:

def get_rank(x):
    if 1 <= x < 96:
        return 1
    elif 96 <= x < 193:
        return 2
    elif 193 <= x < 289:
        return 3
    elif 289 <= x <= 385:
        return 4
    elif x > 385:
        return 5

I have tried to apply the function using lambda:

ranked.apply(lambda x: get_rank(x))

However it gives me the error message:

The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

The end goal is to have a 1 for all values in the table that are below 96, a 2 for all values higher than 192 and smaller than 289 …. and so on up to 5.

Could you please give me a hint how I can easily apply this function to the table?
Appreciate your help!

Solution

Use applymap instead:

>>> ranked[['MMM','AOS','ABT']].applymap(get_rank)

Should return the sub-dataframe "MMM, AOS, ABT" resulting from applying your get_rank() function to each value.

Answered By – Brandt

Answer Checked By – Pedro (BugsFixing Volunteer)