Omid - Challenge 307

data-challenges
advanced-exercises
🔰 Group Custom Grouping!
Published

March 24, 2026

Illustration for Omid - Challenge 307

Challenge Description

🔰 Group Custom Grouping!

Solutions

library(tidyverse)
library(readxl)

path = "files/300-399/307/CH-307 Custom Grouping.xlsx"
input = read_excel(path, range = "B2:C19")
test  = read_excel(path, range = "G2:H4")

result = input %>%
  mutate(Group = (row_number() - 1) %% 2 + 1) %>%
  summarise(`Total Sales` = sum(Sales), .by = Group) 

all.equal(result, test)
# [1] TRUE

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

    • Builds the intermediate columns that drive the final result

  • Strengths:

    • The R solution stays close to the workbook rule and keeps the transformation compact.

  • Areas for Improvement:

    • The code assumes the sheet structure and source ranges remain stable.

  • Gem:

    • The strongest part of the solution is choosing the right intermediate representation before shaping the final output.
import pandas as pd

path = "300-399/307/CH-307 Custom Grouping.xlsx"
input = pd.read_excel(path, usecols="B:C", skiprows=1, nrows=17)
test = pd.read_excel(path, usecols="G:H", skiprows=1, nrows=2)

result = (
    input.assign(Group=(input.index % 2) + 1)
    .groupby('Group', as_index=False)['Sales'].sum()
    .rename(columns={'Sales': 'Total Sales'})
)

print(result.equals(test)) # True

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

    • Builds the intermediate columns that drive the final result

  • Strengths:

    • The Python version follows the same rule in a direct dataframe-oriented implementation.

  • Areas for Improvement:

    • The code assumes the workbook layout remains stable, so any sheet redesign would require small adjustments.

  • Gem:

    • The implementation stays close to the original workbook rule instead of adding unnecessary abstraction.

Difficulty Level

This task is moderate:

  • The business rule is readable, but the workbook still requires careful implementation to reach the expected layout.