Omid - Challenge 309

data-challenges
advanced-exercises
🔰 : Advanced Filtering!
Published

March 24, 2026

Illustration for Omid - Challenge 309

Challenge Description

🔰 : Advanced Filtering!

Solutions

library(tidyverse)
library(readxl)
library(slider)
library(zoo)

path = "files/300-399/309/CH-309 Advanced Filtering.xlsx"
input = read_excel(path, range = "B2:C17")
test  = read_excel(path, range = "G2:H6")

# Solution - classic with lag/lead
result1 = input %>%
  filter(Sales >= lag(Sales) & Sales >= lead(Sales))

# Solution - with zoo::rollapply
result2 = input %>%
  filter(Sales == rollapply(Sales, 3, max, align = "center", fill = NA))

# Solution - with slider::slide_dbl
result3 = input %>%
  filter(Sales == slide_dbl(Sales, ~max(.x), .before = 1, .after = 1))

all.equal(result, test)
# [1] TRUE
all.equal(result2, test)
# [1] TRUE
all.equal(result3, test)
# [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 = "300-399/309/CH-309 Advanced Filtering.xlsx"
df = pd.read_excel(path, usecols="B:C", skiprows=1, nrows=15)
test = pd.read_excel(path, usecols="G:H", skiprows=1, nrows=4).rename(columns=lambda col: col.replace('.1', ''))

result = df[df.Sales == df.Sales.rolling(3, center=True).max()].dropna().reset_index(drop=True)
print(result.equals(test))

  • 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.