CODEWITHSUNDEEP
pythonpandasdataframe
Wayne2
Wayne2

Reputation: 23

Select n-th lowest value from DataFrame (Every Row!)

I am looking for a solution to pick values (row wise) from a Dataframe. Here is what I already have:

np.random.seed(1)
df = pd.DataFrame(np.random.randint(1,10, (10, 10)))
df.columns = list('ABCDEFGHIJ')

N = 2
idx = np.argsort(df.values, 1)[:, 0:N]

df= pd.concat([pd.DataFrame(df.values.take(idx), index=df.index), pd.DataFrame(df.columns[idx], index=df.index)],keys=['Value', 'Columns']).sort_index(level=1)

Now I have the index/position for every value but if I try to get the values from the Dataframe it only takes the values from the first row. What do I have to change in the code?

df looks like:

   A  B  C  D  E  F  G  H  I  J
0  6  9  6  1  1  2  8  7  3  5
1  6  3  5  3  5  8  8  2  8  1
2  7  8  7  2  1  2  9  9  4  9
....

My output should look like:

0  D E
0  1 1
1  J H
1  1 2

Upvotes: 2

Views: 213

Answers (1)

Ch3steR
Ch3steR

Reputation: 20669

You can use np.take_along_axis to take values from dataframe. Use np.insert to sieve both values taken and corresponding column names.

# idx is the same as the one used in the question.

vals = np.take_along_axis(df.values, idx, axis=1)
cols = df.columns.values[idx]
indices = np.r_[: len(vals)] # same as np.arange(len(vals))

out = np.insert(vals.astype(str), indices , cols, axis=0)
index = np.repeat(indices, 2)
df = pd.DataFrame(out, index=index)

   0  1
0  D  E
0  1  1
1  J  H
1  1  2
2  E  D
2  1  2
3  E  I
3  2  2
4  A  D
4  1  1
5  I  J
5  1  3
6  E  I
6  1  2
7  B  H
7  1  3
8  G  I
8  1  1
9  E  A
9  1  2

Upvotes: 2

Related Questions