Module # 12 R Markdown

---

title: "Markdown Assignment for LIS4370"

author: "Issaiah Jennings"

date: "2025-04-13"

output: html_document

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## Introduction

In this project, I worked on functions that help analyze student grade data. I used R to build functions that calculate averages, give letter grades, and filter students who are doing well. This file explains what each function does, how it works, and includes example code.

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## Function 1: `average_grade()`

**What it does:**  

Takes a list of grades and gives back the average.

**Inputs:**  

- A vector of numbers (grades)

**Outputs:**  

- One number (the average)

**Code:**

```{r}

average_grade <- function(grades) {

  return(mean(grades, na.rm = TRUE))

}

# Example

average_grade(c(90, 85, 88))      # 87.67

average_grade(c(100, 95, NA, 85)) # 93.33

Function 2: get_letter_grade()

What it does:
Turns a number grade into a letter grade.

Inputs:

• A number (like 87.67)

Outputs:

• A letter (like "B")

Code:

{r}

get_letter_grade <- function(avg) {
  if (avg >= 90) {
    return("A")
  } else if (avg >= 80) {
    return("B")
  } else if (avg >= 70) {
    return("C")
  } else if (avg >= 60) {
    return("D")
  } else {
    return("F")
  }
}

# Example
get_letter_grade(87.67)  # "B"
get_letter_grade(59)     # "F"

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Function 3: filter_high_performers()

What it does:
Keeps only students who scored above a certain average.

Inputs:

• A data frame with a column called average

• A number (threshold)

Outputs:

• A smaller data frame with students who passed the threshold

Code:

{r}

filter_high_performers <- function(df, threshold) {
  return(df[df$average > threshold, ])
}

# Example
students <- data.frame(
  name = c("Alex", "Jordan", "Taylor"),
  average = c(92, 78, 88)
)

filter_high_performers(students, 85)

R Markdown made it easy to keep my code, notes, and examples all in one place. I didn’t need to switch between files. I could just write and run everything here.

This file shows the three main functions I used for my grade analysis project. It’s clean and easy to read, and it’ll be helpful when I post it on GitHub. This was a good way to get better at coding and documenting my work.

https://github.com/Ijennin/R-Functions/blob/main/Grade_Average_Calculator.Rmd

https://github.com/Ijennin/R-Functions/blob/main/Grade_Average_Calculator.html

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