Exercise

# Histogram of p-values

A good diagnostic plot is the histogram of p-values. A large density of low p-values indicates many differentially expressed genes; whereas, a uniformly distributed histogram indicates there are few. Create a p-value histogram for the leukemia study.

Instructions

**100 XP**

The fitted model object of the leukemia study from Chapter 2, `fit2`

, has been loaded in your workspace. The limma package is already loaded.

Use

`topTable`

to obtain the summary statistics for every gene.To obtain results for every gene, set the argument

`number`

to be the number of rows of`fit2`

.To disable sorting the results by significance level, set the argument

`sort.by`

to`"none"`

.Use

`hist`

to create a histogram of p-values.