## -----------------------------------------------------------------------------
head(mtcars)

## -----------------------------------------------------------------------------
our.data <- mtcars
our.data$mpg[5] <- our.data$mpg[5] * -1
our.data[4:6,]

## ----message=FALSE------------------------------------------------------------
library(dplyr)

our.data %>%
  group_by(cyl) %>%
  summarise(avg.mpg=mean(mpg))


## -----------------------------------------------------------------------------
not.empty.p <- function(x) if(x=="") return(FALSE)

## -----------------------------------------------------------------------------
seven.digit.p <- function(x) nchar(x)==7

## ----perl=FALSE---------------------------------------------------------------
example.data <- data.frame(x=c(8, 9, 6, 5, 9, 5, 6, 7,
                             8, 9, 6, 5, 5, 6, 7),
                         y=c(82, 91, 61, 49, 40, 49, 57,
                             74, 78, 90, 61, 49, 51, 62, 68))
(example.data)