Omid - Challenge 155

data-challenges
advanced-exercises
🔰 Table Transformation!
Published

March 24, 2026

Illustration for Omid - Challenge 155

Challenge Description

🔰 Table Transformation!

Solutions

library(tidyverse)
library(readxl) 
library(janitor)

path = "files/CH-155 Table Transformation.xlsx"
input = read_excel(path, range = "C2:E23")
test  = read_excel(path, range = "G2:I11")

result = input %>%
  mutate(Description = lead(Description), 
         Qty = lead(Qty,2) %>% as.character()) %>%
  remove_empty("rows") %>%
  replace_na(list(Qty = "-")) %>%
  fill(Date, .direction = "down")

all.equal(result[2:3], test[2:3], check.attributes = FALSE)  
# [1] TRUE

# structure correct, have some problems with date

  • 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-155 Table Transformation.xlsx"
input = pd.read_excel(path, usecols="C:E", skiprows=1, nrows=21)
test = pd.read_excel(path, usecols="G:I", skiprows=1, nrows=10)
test.columns = input.columns

input.columns = ["Date", "Description", "Qty"]
input["Date"] = input["Date"].ffill()
input["Description"] = input["Description"].shift(-1)
input["Qty"] = input["Qty"].shift(-2)
input.loc[(input["Description"].notna()) & (input["Qty"].isna()), "Qty"] = "-"
input.dropna(inplace=True)
input["Date"] = pd.to_datetime(input["Date"]).dt.strftime('%d-%m-%Y')
input.reset_index(drop=True, inplace=True)

# had the same values, but cannot convert to common format. :D
print(input)

  • 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.