Omid - Challenge 14

data-challenges
advanced-exercises
🔰 Create a list of products sold in all the months throughout the year.
Published

March 24, 2026

Illustration for Omid - Challenge 14

Challenge Description

🔰 Create a list of products sold in all the months throughout the year.

Solutions

library(tidyverse)
library(readxl)

input = read_excel("files/CH-014.xlsx", range = "B2:D133")
test  = read_excel("files/CH-014.xlsx", range = "K2:K5")

result = input %>%
  mutate(month = month(Date)) %>%
  group_by(Product) %>%
  summarise(nm = n_distinct(month)) %>%
  filter(nm == 12) %>%
  ungroup() %>%
  select(Products = Product)

identical(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

input_data = pd.read_excel("CH-014.xlsx", usecols="B:D", skiprows=1, nrows=132)
test = pd.read_excel("CH-014.xlsx", usecols="K", skiprows=1, nrows=4)

input_data["Date"] = pd.to_datetime(input_data["Date"])
result = (
    input_data.assign(month=input_data["Date"].dt.month)
    .groupby("Product", as_index=False)["month"]
    .nunique()
)
result = result.loc[result["month"] == 12, ["Product"]].rename(columns={"Product": "Products"})

print(result.equals(test))

  • 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 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.