CODEWITHSUNDEEP
pythonpandas
Suraj Shejal
Suraj Shejal

Reputation: 650

Find nearest from given list for entire column

I have a list of some numbers. I want to find closest value from list for entire column:

mylist=[11,44,23,66,100]
df = pd.DataFrame(data={'Data':[11,22,33,43,52,63]})
df>>
    Data
0   11
1   22
2   33
3   43
4   52
5   63

My desired output:

    Data    Nearest
0   11      11
1   22      23
2   33      23
3   43      44
4   52      66
5   63      66

I have tried by using min function with iteraration but its slow

Upvotes: 0

Views: 113

Answers (3)

Mohamed Thasin ah
Mohamed Thasin ah

Reputation: 11192

This could work,

def nearest(a, x):
    n = [abs(i-x) for i in a]
    idx = n.index(min(n))
    return a[idx]

def nearest_alternative(a, v):
    idx = (np.abs(a-v)).argmin()
    return array[idx]

df['nearest'] = df['Data'].apply(lambda x: nearest(mylist, x))

alternative:

O/P:

   Data  nearest
0    11       11
1    22       23
2    33       23
3    43       44
4    52       44
5    63       66

Explanation:

  • nearest function will receive mylist and each element of Data.
  • Compute difference between x and mylist
  • Return element which has minimum value

Upvotes: 0

wwnde
wwnde

Reputation: 26676

df1=pd.DataFrame(mylist,columns=['Nearest']).sort_values(by='Nearest')#Create DataFrame from list

pd.merge_asof(df, df1,left_on="Data", right_on="Nearest",direction="forward")#Merge asof

    Data  Nearest
0    11       11
1    22       23
2    33       44
3    43       44
4    52       66
5    63       66

Or

print(pd.merge_asof(df, df1,left_on="Data", right_on="Nearest",direction="nearest"))



    Data  Nearest
0    11       11
1    22       23
2    33       23
3    43       44
4    52       44
5    63       66

Upvotes: 2

ThePyGuy
ThePyGuy

Reputation: 18446

You can use apply and pass a lambda function which takes gives the index with minimum absolute difference, then just take the item from the list for that index.

df['Nearest'] = df['Data'].apply(lambda x: mylist[(min([(idx,abs(x - v)) for idx, v in enumerate(mylist)], key= lambda x: x[1]))[0]])


   Data  Nearest
0    11       11
1    22       23
2    33       23
3    43       44
4    52       44
5    63       66

Upvotes: 0

Related Questions