Assignment 8

 

Assignment 8 — Input/Output, String Manipulation, and the plyr Package

Objectives

This assignment focused on using R to handle input/output operations, perform data summarization using the plyr package, and apply string manipulation techniques.
By completing this exercise, I learned how to import data files, compute grouped statistics, filter data based on character patterns, and export processed results in multiple formats.

R Code

# Step 1: Import dataset into R
# Choose file interactively or specify directly
student6 <- read.table(
  file.choose(),    
  header = TRUE,
  sep = ",",
  stringsAsFactors = FALSE
)

# Step 2: Install and load plyr package
install.packages("plyr")
library(plyr)
# Compute mean Grade by Sex
gender_mean <- ddply(
  student6,
  "Sex",
  summarise,
  GradeAverage = mean(Grade, na.rm = TRUE)
)

# Step 3: Write the grouped means to a text file
write.table(
  gender_mean,
  file = "gender_mean.txt",
  sep = "\t",
  row.names = FALSE
)

# Step 4: Filter names containing the letter "i" (case-insensitive)
i_students <- subset(
  student6,
  grepl("i", Name, ignore.case = TRUE)
)

# Step 5: Write only the names to a CSV file
write.csv(
  i_students$Name,
  file = "i_students.csv",
  row.names = FALSE,
  quote = FALSE
)

# Step 6: Write the full filtered dataset to another CSV
write.csv(
  i_students,
  file = "i_students_full.csv",
  row.names = FALSE
)

# Step 7: Confirm files exist in working directory
cat("Files successfully created in:", getwd(), "\n")
list.files(pattern = "gender_mean|i_students")

Output:


The console confirms all three output files (gender_mean.txt, i_students.csv, i_students_full.csv) exist in the working directory.

i_students_full.csv

i_students.csv

gender_mean.txt

Summary

This assignment strengthened my understanding of file operations and text processing in R.
It demonstrated how to automate data summarization, apply string-based filters, and produce clean, shareable output files — essential skills for efficient data analysis and reproducibility.

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