How to select rows in Pandas dataframe where value appears more than once

You can use value_counts + isin –

v = df.Parameter.value_counts()
df[df.Parameter.isin(v.index[v.gt(5)])]

For example, where K = 2 (get all items which have more than 2 readings) –

df

   ID Parameter  Value
0   0         A    4.3
1   1         B    3.1
2   2         C    8.9
3   3         A    2.1
4   4         A    3.9
5   5         B    4.5

v = df.Parameter.value_counts()
v

A    3
B    2
C    1
Name: Parameter, dtype: int64

df[df.Parameter.isin(v.index[v.gt(2)])]

   ID Parameter  Value
0   0         A    4.3
3   3         A    2.1
4   4         A    3.9