Omid - Challenge 168

data-challenges
advanced-exercises
🔰 Group 68: Custom Grouping!
Published

March 24, 2026

Illustration for Omid - Challenge 168

Challenge Description

🔰 Group 68: Custom Grouping!

Solutions

library(tidyverse)
library(readxl)

path = "files/CH-168 Custom Grouping.xlsx"
input = read_excel(path, range = "B2:C26")
test  = read_excel(path, range = "G2:I26")

result = input %>%
  mutate(group = cumsum(cummin(`Stock price`) != lag(cummin(`Stock price`), default = first(cummin(`Stock price`)))) + 1)

all.equal(result, test, check.attributes = FALSE)
#> [1] TRUE

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • 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 = "CH-168 Custom Grouping.xlsx"
input = pd.read_excel(path, usecols="B:C", skiprows=1, nrows=25)
test = pd.read_excel(path, usecols="G:I", skiprows=1, nrows=25).rename(columns=lambda x: x.split('.')[0])

input['Group'] = ((input['Stock price'].cummin() != input['Stock price'].cummin().shift().fillna(input['Stock price'].cummin().iloc[0])).cumsum() + 1)

print(all(input == test)) # True

  • Logic:

    • Reads the workbook ranges needed for the challenge

  • 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.