---
title: "Session 1 — A simple function"
subtitle: "QSS 1.3.6 | Probability and Statistics (MIR)"
author: "Prof. Dae-Jin Lee (daelee@faculty.ie.edu)"
date: "Fall 2026"
output:
  html_document:
    toc: true
    toc_float: true
    theme: flatly
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE, message = FALSE, warning = FALSE)
```

```{r}
world.pop <- c(2525779, 3026003, 3691173, 4449049, 5320817, 6127700, 6916183)

my.summary <- function(x) {
  s.out <- sum(x)
  l.out <- length(x)
  m.out <- s.out / l.out
  out <- c(s.out, l.out, m.out)
  names(out) <- c("sum", "length", "mean")
  return(out)
}
my.summary(1:10)
my.summary(world.pop)
```

**Interpret:** The function returns sum, length, and mean. Confirm the mean matches `mean(world.pop)`.