In abrown435/immunarch-test: Bioinformatics Analysis of T-Cell and B-Cell Immune Repertoires

```r

knitr::knit_hooks$set(optipng = knitr::hook_optipng)

knitr::opts_chunk$set(optipng = '-o7')

knitr::opts_chunk$set(echo = TRUE) knitr::opts_chunk$set(fig.align = "center") knitr::opts_chunk$set(fig.width = 12) knitr::opts_chunk$set(fig.height = 5)

library(immunarch) data(immdata)

# Kmer statistics computation

Counting kmer occurrences in `immunarch` is very easy. All you need to do is to run the `getKmers()` function on your data:

```r
kmers <- getKmers(immdata$data[[1]], 3)
kmers

If is possible to compute occurrences of kmers in a batch of immune repertoires. In order to do that, you just need to provide a list of immune repertoires to the function. NA means that there is no such kmer found in a sample, specifyed by the column name.

kmers <- getKmers(immdata$data, 5)
kmers

Note that by default getKmers() filter out all non-coding sequences before counting the kmer statistics. You can use both coding and non-coding sequences by setting the .coding argument to FALSE:

kmers <- getKmers(immdata$data[[1]], 3, .coding = F)
kmers

Kmer statistics visualisation

To visualise your kmer statistics, the vis() function comes to help:

kmers <- getKmers(immdata$data, 5)
vis(kmers)

The vis() function for kmers has a number of arguments to manipulate the plot. First, the .head argument specifies the number of the most abundant kmers to visualise.

p1 <- vis(kmers, .head = 5)
p2 <- vis(kmers, .head = 10)
p3 <- vis(kmers, .head = 30)

(p1 + p2) / p3

Second, there are three options to choose from for positions of bars: "stack", "dodge" and "fill", adjusted by providing the correposnding option to the .position argument:

p1 <- vis(kmers, .head = 10, .position = "stack")
p2 <- vis(kmers, .head = 10, .position = "fill")
p3 <- vis(kmers, .head = 10, .position = "dodge")

(p1 + p2) / p3

Option "stack" stacks all bars on top of each other so you can see the full distribution of kmers. Option "fill" stack all bars on top of each other as well, but normalises it in a such way so you see distribution of counts per-kmer, i.e., you can clearly see which repertoire has more kmer counts than others for a specific kmer. Option "dodge" groups kmer bars of different samples so you can clearly see, which samples has more kmer occurrences overall.

Additional argument is .log needed if your distribution of kmer counts is vastly imbalanced for some of repertoires. It permits to use the log-transformation of y-axis so you can see differences in orders of magnitude in kmer counts rather.

p1 <- vis(kmers, .head = 10, .position = "stack")
p2 <- vis(kmers, .head = 10, .position = "stack", .log = T)

p1 + p2

Sequence motifs analysis

immunarch utilises common approaches to sequence motif analysis and uses different types of matrices to represent sequence motifs:

• position frequency matrix (PFM) - a matrix with occurences of each amino acid in each position;
• position probability matrix (PPM) - a matrix with probabilities of occurences of each amino acid in each position;
• position weight matrix (PWM) - a matrix with log likelihoods of PPM elements;
• a matrix with self-information of elements in PWM.

To compute and visualise sequence motifs, first you need to compute kmer statistics for one of the input immune repertoires, and then apply the kmer_profile() function to compute sequence motif matrices:

kmers <- getKmers(immdata$data[[1]], 5)
kmer_profile(kmers)

Currently we are not supporting sequence motifs analysis for more than one sample, but we are working on it. In order to compute and visualise sequence motif matrices for all of your samples you need to process them one-by-one, which can be easily done in for-loops or via the lapply() function.

Argument .method specifies which matrix to compute:

• .method = "freq" - position frequency matrix (PFM);
• .method = "prob" - position probability matrix (PPM);
• .method = "wei" - position weight matrix (PWM);
• .method = "self" - self-information matrix.

kmer_profile(kmers, "freq")
kmer_profile(kmers, "prob")
kmer_profile(kmers, "wei")
kmer_profile(kmers, "self")

Sequence motif visualisation

Visualisation of sequence motif matrices is done by vis(). There are two types of plots to choose from - sequence logo and "text logo". The argument .plot regulates the type of plot: .plot = "seq" for sequence logo plots and .plot = "text" (by default) for "text logo" plots.

kp <- kmer_profile(kmers, "self")
p1 <- vis(kp)
p2 <- vis(kp, .plot = "seq")

p1 + p2

Get in contact with us

Can not find an important feature? Have a question or found a bug? Contact us at [e-mail]

abrown435/immunarch-test documentation built on July 29, 2020, 12:04 a.m.