R notes for Activity 10-5: Digital Cameras
As always, we start by reading in some values.
DC = read.csv("/home/rebelsky/Stats115/Data/DigitalCameras.csv")
head(DC)
As that summary suggests, the five columns in the table are
Brand, Model, Type, Price,
Score. Now, the book asks us to separate them by
type. Lets check what kinds of types there are.
summary(DC$Type)
Well, it looks the the four types are
advanced compact,
compact,
subcompact, and
super-zoom. Each is probably represented as
a string.
a. Segmenting and Summarizing
This problem asks us to summarize the data by type of camera.
In order to get summaries, we need to break apart the data according
to type. Let's start by creating a vector of prices for each of the
four kinds of camera. Note that the price is is column 4, so we can
use a selector to get the appropriate rows and then just take column 4.
From that vector, we compute the six-number summary.
summary(DC[DC$Type=="advanced compact", 4])
summary(DC[DC$Type=="compact", 4])
summary(DC[DC$Type=="subcompact", 4])
summary(DC[DC$Type=="super-zoom", 4])
In addition to those summaries, we might make boxplots.
If we're going to do aligned boxplots, we need a way to
join those boxplots together. Alternately we can look for
a command to draw multiple boxpots, stacked on top of each
other. Fortunately, the split operation
comes into play here.
boxplot(split(DC$Price,DC$Type), horizontal=T)
Exercise d: Comparing Ratings
You may recall that we recently split prices by type. Here, we want to split
the
Score column. The particulars of that command are left
as an exercise for the reader.
