---
title: "Control Structures and Loops"
output: html_notebook
---

## if-else

```{r}
#if (test_expression) {
#statement
#}

x <- 5
if(x > 0)
{
  print("Positive number")
}

```

```{r}
# if (test_expression) 
# {
#   statement1
# } 
# else
# {
#   statement2
# }
x <- -5
if(x > 0)
{
  print("Non-negative number")
} else 
{
  print("Negative number")
}
# if ( test_expression1) {
# statement1
# } else if ( test_expression2) {
# statement2
# } else if ( test_expression3) {
# statement3
# } else {
# statement4
# }
```

## loops

### for

```{r}
for (year in 2010:2015){
  print(paste("The year is", year))
}
```


```{r}
years = c(2010,2011,2012,2013,2014,2015)
for (i in 1:length(years))
{
  if (i > 2)
  {
    print(paste("The year is", years[i]))
  }
}
```

### while

```{r}
i <- 1
while (i < 6) {
  print(i)
  i = i + 1 # important!
  # break # stops loops
}
```

```{r}
i <- 1
while (TRUE) { # forever!
  print(i)
  i = i * 2
  if (i > 10)
  {
    break # exit loop
  }
}
```

or

```{r}
i <- 1
repeat{
  print(i)
  i = i * 2
  if (i > 10)
  {
    break # exit loop
  }
}
```