Omid - Challenge 158

data-challenges
advanced-exercises
🔰 : Filter Last Transaction!
Published

March 24, 2026

Illustration for Omid - Challenge 158

Challenge Description

🔰 : Filter Last Transaction!

Solutions

library(tidyverse)
library(readxl)

path = "files/CH-158 Filter the last transaction in mounth.xlsx"
input = read_excel(path, range = "B2:D14")
test  = read_excel(path, range = "F2:H6")

result = input %>% 
  group_by(`Product ID`, month = month(Date)) %>%
  filter(Date == max(Date)) %>%
  ungroup() %>%
  select(-month)

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

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

  • 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-158 Filter the last transaction in mounth.xlsx"
input = pd.read_excel(path, usecols="B:D", skiprows=1, nrows=12)
test = pd.read_excel(path, usecols="F:H", skiprows=1, nrows=4).rename(columns=lambda x: x.split('.')[0])

input['Date'] = pd.to_datetime(input['Date'])
input['month'] = input['Date'].dt.month

result = input.loc[input.groupby(['Product ID', 'month'])['Date'].idxmax()].sort_values(by='Date').reset_index(drop=True).drop(columns=['month'])

print(result.equals(test)) # True

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

  • 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 core logic is clear, but the correct transformation pattern is not obvious from the raw input.

  • The challenge combines multiple reshaping, grouping, or parsing steps.