Fix my code

Intro

We are working with the iris dataset today

# this is to make the iris dataset show up in the R environement 
iris = iris

# Get an overview of the iris dataset 
summary(iris)

Exercise 1

# Why is this code not working? 
  #We know the length should be 150 from looking at the data in the Environement 
length(iris$species)

Exercise 2

# calculate the median iris$Species

Exercise 3

# install the package if you need to
#install.packages("plyr")

# run the code below as is. 
# load plyr package 
library(plyr)
# Check that plyr is loaded in your packages tab  

# create a new dataframe that is the iris dataset summarized
iris.summarized = ddply(iris, # take the iris dataset
                        c("Species"), # for each Species
                        summarise, # summarize the 
                        mean.sl = mean(Sepal.Length), # mean Sepal.Length 
                        min.sl = min(Sepal.Length), # minumum Sepal.Length
                        max.sl = max(Sepal.Length)) # maximum Sepal.Length

# check that iris.summarized is in your R environement 


# let's say we are curious about Sepal.Width now
print(iris.summarized$max.sw)
# it prints NULL

Answers

Click the dropdown to reveal the answers

Exercise 1

Species needs to be capitalized.

length(iris$Species)

Exercise 2

Error in median.default(iris$Species) : need numeric data

Species is a character variable, not numeric

You can't do this because it does not make sense to calculate the median of a list of species names. The code below calculates the median for the Sepal.Length column

median(iris$Sepal.Length)

Exercise 3

We did not include sepal width in our iris.summarized data so R does not know what you are asking it for.

It is saying, this does not exist.

This can be solved by switching our question to Sepal.Length

print(iris.summarized$max.sl)

ouput [1] 5.8 7.0 7.9