---
title: "Homework 1 Solutions"
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
# Ch. 2, Q1
```{r}
x <- c("economics", "econometrics", "ECON 4750")
library(stringr)
str_length(x)
```
# Ch. 2, Q3
**Part a**
```{r}
fibonacci <- function(n) {
# handle cases where n=1 or 2
if (n == 1) {
return(0)
}
if (n==2) {
return(1)
}
# main code
fib_seq <- c(0,1)
for (i in 3:n) {
fib_seq[i] <- fib_seq[i-1] + fib_seq[i-2]
}
fib_seq[n]
}
```
```{r}
fibonacci(5)
fibonacci(8)
```
**Part b**
```{r}
alt_seq <- function(a,b,n) {
# handle cases where n=1 or 2
if (n == 1) {
return(a)
}
if (n==2) {
return(b)
}
# main code
this_seq <- c(a,b)
for (i in 3:n) {
this_seq[i] <- this_seq[i-1] + this_seq[i-2]
}
this_seq[n]
}
```
```{r}
alt_seq(3,7,4)
```
# Ch. 2, Q5
**Part a**
```{r}
nrow(iris)
```
**Part b**
```{r}
mean(iris$Sepal.Length)
```
**Part c**
```{r}
mean(subset(iris, Species=="setosa")$Sepal.Width)
```
**Part d**
```{r}
sorted_iris <- iris[order(iris$Petal.Length),]
sorted_iris[1:10,]
```