# Interactive Q-Q Plots in R using Plotly

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### Introduction

In a recent blog post, I introduced the new R package, manhattanly, which creates interactive manhattan plots using the plotly.js engine.

In this post, I describe how to create interactive Q-Q plots using the manhattanly package. Q-Q plots tell us about the distributional assumptions of the observed test statistics and are common visualisation tools in statistical analyses.

Visit the package website for full details and example usage.

### Quick Start

The following three lines of code will produce the Q-Q plot below

install.packages("manhattanly") library(manhattanly) qqly(HapMap, snp = "SNP", gene = "GENE")

Notice that we have added two annotations (the SNP and nearest GENE), that are revealed when hovering the mouse over a point. This feature of interactive Q-Q plots adds a great deal of information to the plot without cluttering it with text.

### The Data

Inspired by the heatmaply package by Tal Galili, we split the tasks into data pre-processing and plot rendering. Therefore, we can use the `manhattanly::qqr`

function to get the data used to produce a Q-Q plot. This allows flexibility in the rendering of the plot, since any graphics package, such as `plot`

in base R can make used to create the plot.

The plot data is derived using the `manhattanly::qqr`

function:

qqrObject <- qqr(HapMap) str(qqrObject)

```
## List of 6
## $ data :'data.frame': 14412 obs. of 3 variables:
## ..$ P : num [1:14412] 6.75e-10 3.41e-09 3.95e-09 4.71e-09 5.02e-09 ...
## ..$ OBSERVED: num [1:14412] 9.17 8.47 8.4 8.33 8.3 ...
## ..$ EXPECTED: num [1:14412] 4.46 3.98 3.76 3.61 3.51 ...
## $ pName : chr "P"
## $ snpName : logi NA
## $ geneName : logi NA
## $ annotation1Name: logi NA
## $ annotation2Name: logi NA
## - attr(*, "class")= chr "qqr"
```

head(qqrObject[["data"]])

```
## P OBSERVED EXPECTED
## 4346 6.75010e-10 9.170690 4.459754
## 4347 3.41101e-09 8.467117 3.982633
## 4344 3.95101e-09 8.403292 3.760784
## 4338 4.70701e-09 8.327255 3.614656
## 4342 5.02201e-09 8.299122 3.505512
## 4341 6.22801e-09 8.205651 3.418362
```

This `qqrObject`

which is of class `qqr`

can also be passed to the `manhattanly::qqly`

function to produce the inteactive Q-Q plot above:

qqly(qqrObject)

### Related Work

This work is based on the qqman package by Stephen Turner. It produces similar manhattan and Q-Q plots as the `qqman::manhattan`

and `qqman::qq`

functions; the main difference here is being able to interact with the plot, including extra annotation information and seamless integration with HTML.

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