R Homework for April 4, 2013

Section 1: Data Types

Questions 1 to 6 refer to the file ELF3s_bolting_Rclub.csv. Import it now.

Q1

What data types are represented in each column?

Q2

a) Are there any columns that you think have the wrong data type?

b) Which ones?

c) Why?

Q3

How would you change the columns to their correct types?

Q4

Are there any obvious mistakes in this data frame beyond what you might have found in answering Q3?

Q5

Make the “Sha” genotype the reference level for the genotype column

Q6

Change the order of levels in “trasformation” to be Sh1, Sh2, Sh3, Ba1, Ba3

Section 2: Reshape

The remaining questions deal with the reshape package and the tomato dataset.

• Read my post on reshape on the Rclub website
• Additional information on reshape is in section 9.2 of the ggplot book
• import the standard tomato data set.

Q7

What are the id variables and measure variables in the Tomato data set?

Q8

Subset the tomato data set to keep the int1-int4 measurements and the relevant metadata.

Q9

Without melting or casting your new data frame, calculate the mean of each internode. Hint: use apply()

Q10

Melt the new data frame.

Q11

Use cast to obtain the mean for each internode.

Q12

Use cast to obtain the mean for each internode for each species.

Q13

Use cast to obtain the mean for each internode for each species under each treatment.

Q14

Create a boxplot for each combination of species, internode, and treatment.