Author: David Clausen, Sarah Teichman and Amy Willis
Date: 2026-04-02

# Introduction to radEmu with TreeSummarizedExperiment

#### David Clausen, Sarah Teichman and Amy Willis

#### 2026-04-02

First, we will install `radEmu`, if we haven’t already.

    # if (!require("remotes", quietly = TRUE))
    #     install.packages("remotes")
    #
    # remotes::install_github("statdivlab/radEmu")

Next, we can load `radEmu` as well as the `tidyverse` package suite.

    library(magrittr)
    library(dplyr)
    library(ggplot2)
    library(stringr)
    library(radEmu)

## Introduction

This vignette provides an introduction to using `radEmu` for differential abundance analysis using a `TreeSummarizedExperiment` data object. For more in-depth explanations of how this software works, an example of running hypothesis tests, and details on this analysis, see the vignette “intro_radEmu.Rmd”.

In this lab we’ll explore a dataset published by Wirbel et al. (2019). This is a meta-analysis of case-control studies, meaning that Wirbel et al. collected raw sequencing data from studies other researchers conducted and re-analyzed it (in this case, they also collected some new data of their own).

Wirbel et al. published two pieces of data we’ll focus on today:

- metadata giving demographics and other information about participants
- a mOTU (metagenomic OTU) table

In the manuscript, we looked at differential abundance across otherwise similar colorectal cancer and non-cancer control study participants for the 849 mOTUs that Wirbel et al. published. For the purpose of having a streamlined tutorial, we will only look at a subset of those 849 mOTUs in this vignette.

## Loading and exploring data

Note that in order to follow along with this tutorial (but not to use `radEmu`!) you will need to have `TreeSummarizedExperiment` installed. We will check if you have `TreeSummarizedExperiment` installed, and if you do not then you can read the following code but it will not be run.

    tse <- requireNamespace("TreeSummarizedExperiment", quietly = TRUE) == TRUE

    #> [1] "TreeSummarizedExperiment is installed: TRUE"

Now that we have loaded the `TreeSummarizedExperiment` package, we will create our `TreeSummarizedExperiment` data object.

    library(TreeSummarizedExperiment)
    library(SummarizedExperiment)
    library(SingleCellExperiment)
    setClassUnion("ExpData", c("matrix", "SummarizedExperiment"))

    data(wirbel_sample)
    data(wirbel_otu)
    data(wirbel_taxonomy)
    wirbel_tse <- TreeSummarizedExperiment(assays = list(Count = t(wirbel_otu)),
                                           rowData = wirbel_taxonomy,
                                           colData = wirbel_sample)
    wirbel_tse
    #> class: TreeSummarizedExperiment
    #> dim: 845 566
    #> metadata(0):
    #> assays(1): Count
    #> rownames(845): Streptococcus anginosus [ref_mOTU_v2_0004]
    #>   Enterobacteriaceae sp. [ref_mOTU_v2_0036] ... unknown Clostridiales
    #>   [meta_mOTU_v2_7795] unknown Clostridiales [meta_mOTU_v2_7800]
    #> rowData names(7): domain phylum ... genus species
    #> colnames(566): CCIS00146684ST.4.0 CCIS00281083ST.3.0 ... SAMEA3178940
    #>   SAMEA3178943
    #> colData names(14): Sample_ID External_ID ... BMI_spline.2 Sampling
    #> reducedDimNames(0):
    #> mainExpName: NULL
    #> altExpNames(0):
    #> rowLinks: NULL
    #> rowTree: NULL
    #> colLinks: NULL
    #> colTree: NULL

We’ll start by looking at the metadata.

    dim(colData(wirbel_tse))
    #> [1] 566  14
    head(colData(wirbel_tse))
    #> DataFrame with 6 rows and 14 columns
    #>                             Sample_ID External_ID       Age      Gender
    #>                           <character> <character> <integer> <character>
    #> CCIS00146684ST.4.0 CCIS00146684ST-4-0      FR-726        72           F
    #> CCIS00281083ST.3.0 CCIS00281083ST-3-0      FR-060        53           M
    #> CCIS02124300ST.4.0 CCIS02124300ST-4-0      FR-568        35           M
    #> CCIS02379307ST.4.0 CCIS02379307ST-4-0      FR-828        67           M
    #> CCIS02856720ST.4.0 CCIS02856720ST-4-0      FR-027        74           M
    #> CCIS03473770ST.4.0 CCIS03473770ST-4-0      FR-192        29           M
    #>                          BMI     Country       Study       Group Library_Size
    #>                    <numeric> <character> <character> <character>    <integer>
    #> CCIS00146684ST.4.0        25         FRA      FR-CRC         CTR     35443944
    #> CCIS00281083ST.3.0        32         FRA      FR-CRC         CTR     19307896
    #> CCIS02124300ST.4.0        23         FRA      FR-CRC         CTR     42141246
    #> CCIS02379307ST.4.0        28         FRA      FR-CRC         CRC      4829533
    #> CCIS02856720ST.4.0        27         FRA      FR-CRC         CTR     34294675
    #> CCIS03473770ST.4.0        24         FRA      FR-CRC         CTR     20262319
    #>                    Age_spline.1 Age_spline.2 BMI_spline.1 BMI_spline.2
    #>                       <numeric>    <numeric>    <numeric>    <numeric>
    #> CCIS00146684ST.4.0   -0.1975543     0.738962    1.1898242    -0.560692
    #> CCIS00281083ST.3.0   -0.0812613    -0.681853   -1.4067931     2.003914
    #> CCIS02124300ST.4.0   -2.1745353    -0.681853    0.4547668    -0.670604
    #> CCIS02379307ST.4.0    0.6746432    -0.149048    0.0769882     0.538425
    #> CCIS02856720ST.4.0   -0.5464333     1.094166    0.4479336     0.172053
    #> CCIS03473770ST.4.0   -2.8722933    -0.681853    0.9526144    -0.670604
    #>                       Sampling
    #>                    <character>
    #> CCIS00146684ST.4.0      BEFORE
    #> CCIS00281083ST.3.0      BEFORE
    #> CCIS02124300ST.4.0      BEFORE
    #> CCIS02379307ST.4.0      BEFORE
    #> CCIS02856720ST.4.0      BEFORE
    #> CCIS03473770ST.4.0      BEFORE

We can see that this dataset includes \(566\) observations and \(14\) variables.

Now let’s look at the mOTU table.

    dim(assay(wirbel_tse, "Count"))
    #> [1] 845 566
    # let's check out a subset
    assay(wirbel_tse, "Count")[1:5, 1:3]
    #>                                                     CCIS00146684ST.4.0
    #> Streptococcus anginosus [ref_mOTU_v2_0004]                           0
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]                            3
    #> Citrobacter sp. [ref_mOTU_v2_0076]                                   0
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079]                  0
    #> Enterococcus faecalis [ref_mOTU_v2_0116]                             0
    #>                                                     CCIS00281083ST.3.0
    #> Streptococcus anginosus [ref_mOTU_v2_0004]                           0
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]                            0
    #> Citrobacter sp. [ref_mOTU_v2_0076]                                   0
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079]                  0
    #> Enterococcus faecalis [ref_mOTU_v2_0116]                             0
    #>                                                     CCIS02124300ST.4.0
    #> Streptococcus anginosus [ref_mOTU_v2_0004]                           2
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]                            5
    #> Citrobacter sp. [ref_mOTU_v2_0076]                                   0
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079]                  0
    #> Enterococcus faecalis [ref_mOTU_v2_0116]                             6

We can see that this table has \(566\) samples (just like the metadata) and \(845\) mOTUs. Let’s save these mOTU names in a vector.

    mOTU_names <- rownames(assay(wirbel_tse, "Count"))

Finally, we can check out the taxonomy table.

    head(rowData(wirbel_tse))
    #> DataFrame with 6 rows and 7 columns
    #>                                                          domain         phylum
    #>                                                     <character>    <character>
    #> Streptococcus anginosus [ref_mOTU_v2_0004]             Bacteria      Bacillota
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]              Bacteria Pseudomonadota
    #> Citrobacter sp. [ref_mOTU_v2_0076]                     Bacteria Pseudomonadota
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079]    Bacteria Pseudomonadota
    #> Enterococcus faecalis [ref_mOTU_v2_0116]               Bacteria      Bacillota
    #> Lactobacillus salivarius [ref_mOTU_v2_0125]            Bacteria      Bacillota
    #>                                                                   class
    #>                                                             <character>
    #> Streptococcus anginosus [ref_mOTU_v2_0004]                      Bacilli
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]           Gammaproteobacteria
    #> Citrobacter sp. [ref_mOTU_v2_0076]                  Gammaproteobacteria
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079] Gammaproteobacteria
    #> Enterococcus faecalis [ref_mOTU_v2_0116]                        Bacilli
    #> Lactobacillus salivarius [ref_mOTU_v2_0125]                     Bacilli
    #>                                                                order
    #>                                                          <character>
    #> Streptococcus anginosus [ref_mOTU_v2_0004]           Lactobacillales
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]           Enterobacterales
    #> Citrobacter sp. [ref_mOTU_v2_0076]                  Enterobacterales
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079] Enterobacterales
    #> Enterococcus faecalis [ref_mOTU_v2_0116]             Lactobacillales
    #> Lactobacillus salivarius [ref_mOTU_v2_0125]          Lactobacillales
    #>                                                                 family
    #>                                                            <character>
    #> Streptococcus anginosus [ref_mOTU_v2_0004]            Streptococcaceae
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]           Enterobacteriaceae
    #> Citrobacter sp. [ref_mOTU_v2_0076]                  Enterobacteriaceae
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079] Enterobacteriaceae
    #> Enterococcus faecalis [ref_mOTU_v2_0116]               Enterococcaceae
    #> Lactobacillus salivarius [ref_mOTU_v2_0125]           Lactobacillaceae
    #>                                                                  genus
    #>                                                            <character>
    #> Streptococcus anginosus [ref_mOTU_v2_0004]               Streptococcus
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]           Enterobacteriaceae
    #> Citrobacter sp. [ref_mOTU_v2_0076]                         Citrobacter
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079]         Klebsiella
    #> Enterococcus faecalis [ref_mOTU_v2_0116]                  Enterococcus
    #> Lactobacillus salivarius [ref_mOTU_v2_0125]              Lactobacillus
    #>                                                                    species
    #>                                                                <character>
    #> Streptococcus anginosus [ref_mOTU_v2_0004]          Streptococcus angino..
    #> Enterobacteriaceae sp. [ref_mOTU_v2_0036]           Enterobacteriaceae b..
    #> Citrobacter sp. [ref_mOTU_v2_0076]                         Citrobacter sp.
    #> Klebsiella michiganensis/oxytoca [ref_mOTU_v2_0079] Klebsiella michigane..
    #> Enterococcus faecalis [ref_mOTU_v2_0116]             Enterococcus faecalis
    #> Lactobacillus salivarius [ref_mOTU_v2_0125]         Ligilactobacillus sa..

## Fitting a model

`radEmu` is a package that can be used to estimate fold-differences in the abundance of microbial taxa between levels of a covariate. In this analysis, the covariate that we are primarily interested in is whether a sample is from a case of colorectal cancer or a control. We will make control (“CTR”) the reference category:

    colData(wirbel_tse)$Group <- factor(colData(wirbel_tse)$Group, levels = c("CTR","CRC"))

While in general we would fit a model to all mOTUs, we are going to subset to some specific genera for the purposes of this tutorial. Let’s look at Eubacterium, Porphyromonas, Faecalibacteria, and Fusobacterium for now.

    chosen_genera <- c("Eubacterium", "Faecalibacterium", "Fusobacterium", "Porphyromonas")
    genera_rows <- rowData(wirbel_tse)$genus %in% chosen_genera
    wirbel_restrict <- wirbel_tse[genera_rows]

Again, while we would generally fit a model using all of our samples, for this tutorial we are only going to consider data from a case-control study from China.

    sample_cols <- colData(wirbel_restrict)$Country == "CHI"
    wirbel_china <- wirbel_restrict[, sample_cols]

Next, we want to confirm that all samples have at least one non-zero count across the categories we’ve chosen and that all categories have at least one non-zero count across the samples we’ve chosen.

    sum(colSums(assay(wirbel_china, "Count")) == 0) # no samples have a count sum of 0
    #> [1] 0
    sum(rowSums(assay(wirbel_china, "Count")) == 0) # one category has a count sum of 0
    #> [1] 1
    category_to_rm <- rowSums(assay(wirbel_china, "Count")) == 0
    wirbel_china <- wirbel_china[!category_to_rm, ]
    sum(rowSums(assay(wirbel_china, "Count")) == 0) # now no categories have a count sum of 0
    #> [1] 0

The function that we use to fit our model is called `emuFit`. It can accept your data in various forms, and here we will show how to use it with a `TreeSummarizedExperiment` object as input.

    ch_fit <- emuFit(formula = ~ Group,
                     Y = wirbel_china,
                     assay_name = "Count",
                     run_score_tests = FALSE)

The way to access estimated coefficients and confidence intervals from the model is with `ch_fit$coef`.

Now, we can easily visualize our results using the `plot.emuFit` function!

    plot(ch_fit)$plots
    #> $p1

If you’d like to see more explanations of the `radEmu` software and additional analyses of this data, check out the vignette “intro_radEmu.Rmd”.