R Basics

Some basic commands in R

R has a number of built in data sets that you may find useful in creating examples and practice problems. To access the list of built in data sets type:

data()

To access a specific data set from this list, type data(Name of Data Set) For example:

data(ChickWeight)

Let’s do some examples with the ChickWeight data set First, open RStudio Then type

data(ChickWeight)
attach(ChickWeight)
head(ChickWeight)

##   weight Time Chick Diet
## 1     42    0     1    1
## 2     51    2     1    1
## 3     59    4     1    1
## 4     64    6     1    1
## 5     76    8     1    1
## 6     93   10     1    1

This will load and attach the data set as well as listing the first several rows. This is a good idea so you can see the types of data in the set.

Now try the following commands:

mean(weight)

## [1] 121.8183

Which will calculate the arithmetic mean of the values of the variable “weight”.

median(weight)

## [1] 103

Which will return the middle value of the scores

range(weight)

## [1]  35 373

Which returns the high and low scores of the variable

quantile(weight)

##     0%    25%    50%    75%   100% 
##  35.00  63.00 103.00 163.75 373.00

Which gives the high score, low score, 25th, 50th, and 75th percentile values

sd(weight)

## [1] 71.07196

var(weight)

## [1] 5051.223

Which return the standard deviation and variance of the weights

summary(weight)

##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    35.0    63.0   103.0   121.8   163.8   373.0

Which returns many of the above values (but not all). You may also want to try some plotting with the built in data sets:

boxplot(weight ~ Diet)

Creates a boxplot of weight as a function of Diet

plot(weight ~ Diet)

Produces the same plot but automatically labels the axes (who knows why)

plot(weight, Diet)

Produces a rather useless scatterplot of the data as there are only four levels of diet

hist(weight)

Produces a histogram of the distribution of weights.

All of these polts can be fine tuned with information which can be found in Mike Marin’s Series 2 R videos.

R Basics

DocP

6/20/2017

Some basic commands in R