Reversing the counting direction of a counter
Question:
I’m trying to reverse the counter of the following count but I don’t know how to do it.
My dataframe looks like this (adf):
Visit – ID
Pos(int)
Title(str)
randomnumber1
1
rstring
randomnumber1
2
rstring
randomnumber2
1
rstring
randomnumber2
2
rstring
randomnumber2
3
rstring
My code looks like the following:
bdf = (adf.assign(col=adf.groupby('Visit - ID').cumcount()+1)
.set_index(['Visit - ID','col'])
.unstack('col')
.sort_index(level=(1,0), axis=1)
)
bdf.columns = [f'{x}{y}' for x,y in bdf.columns]
Output:
Visit – ID
Pos 1
Pos 2
Pos 3
randomnumber1
2
1
NaN
randomnumber2
3
2
1
randomnumber3
3
2
1
randomnumber4
3
2
1
randomnumber5
3
2
1
So the counting is reverse. How do I correct the ‘counting direction’ so that it looks like the following?
Visit – ID
Col 1
Col 2
Col 3
randomnumber1
1
2
3
randomnumber2
1
2
3
randomnumber3
1
2
3
randomnumber4
1
2
3
randomnumber5
1
2
3
Answers:
You can use cumcount(ascending=False):
import pandas as pd
df = pd.DataFrame({
'id': [1, 1, 2, 2, 2]
})
df['cc_asc'] = df.groupby('id').cumcount(ascending=True)
df['cc_desc'] = df.groupby('id').cumcount(ascending=False)
df
# id cc_asc cc_desc
# 0 1 0 1
# 1 1 1 0
# 2 2 0 2
# 3 2 1 1
# 4 2 2 0
I’m trying to reverse the counter of the following count but I don’t know how to do it.
My dataframe looks like this (adf):
| Visit – ID | Pos(int) | Title(str) |
|---|---|---|
| randomnumber1 | 1 | rstring |
| randomnumber1 | 2 | rstring |
| randomnumber2 | 1 | rstring |
| randomnumber2 | 2 | rstring |
| randomnumber2 | 3 | rstring |
My code looks like the following:
bdf = (adf.assign(col=adf.groupby('Visit - ID').cumcount()+1)
.set_index(['Visit - ID','col'])
.unstack('col')
.sort_index(level=(1,0), axis=1)
)
bdf.columns = [f'{x}{y}' for x,y in bdf.columns]
Output:
| Visit – ID | Pos 1 | Pos 2 | Pos 3 |
|---|---|---|---|
| randomnumber1 | 2 | 1 | NaN |
| randomnumber2 | 3 | 2 | 1 |
| randomnumber3 | 3 | 2 | 1 |
| randomnumber4 | 3 | 2 | 1 |
| randomnumber5 | 3 | 2 | 1 |
So the counting is reverse. How do I correct the ‘counting direction’ so that it looks like the following?
| Visit – ID | Col 1 | Col 2 | Col 3 |
|---|---|---|---|
| randomnumber1 | 1 | 2 | 3 |
| randomnumber2 | 1 | 2 | 3 |
| randomnumber3 | 1 | 2 | 3 |
| randomnumber4 | 1 | 2 | 3 |
| randomnumber5 | 1 | 2 | 3 |
You can use cumcount(ascending=False):
import pandas as pd
df = pd.DataFrame({
'id': [1, 1, 2, 2, 2]
})
df['cc_asc'] = df.groupby('id').cumcount(ascending=True)
df['cc_desc'] = df.groupby('id').cumcount(ascending=False)
df
# id cc_asc cc_desc
# 0 1 0 1
# 1 1 1 0
# 2 2 0 2
# 3 2 1 1
# 4 2 2 0