Omid - Challenge 256

data-challenges
advanced-exercises
🔰 Table Transformation!
Published

March 24, 2026

Illustration for Omid - Challenge 256

Challenge Description

🔰 Table Transformation!

Solutions

library(tidyverse)
library(readxl)

path = "files/200-299/256/CH-256 Table Transformation.xlsx"
input = read_excel(path, range = "B2:H6")
test  = read_excel(path, range = "B10:E14")

result = cbind(
    input[1],
    set_names(
        map_dfc(
            c("A", "B", "C"),
            ~ rowSums(input[startsWith(names(input), .x)], na.rm = TRUE)
        ),
        c("A", "B", "C")
    )
)

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

  • Logic:

    • Reads the workbook ranges needed for the challenge

  • 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 = "200-299/256/CH-256 Table Transformation.xlsx"
input = pd.read_excel(path, usecols="B:H", nrows=5, skiprows=1)
test = pd.read_excel(path, usecols="B:E", nrows=5, skiprows=9)

result = (input.groupby('Date').sum()
    .T.groupby(lambda x: x[0]).sum()
    .T.reset_index())
for col in result.columns:
     if col != 'Date':
          result[col] = result[col].astype(int)

print(result.equals(test)) # True

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

    • Applies the rule iteratively until the output stabilizes

  • 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.