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dar

Introduction

Differential abundance testing in microbiome data challenges both parametric and non-parametric statistical methods, due to its sparsity, high variability and compositional nature. Microbiome-specific statistical methods often assume classical distribution models or take into account compositional specifics. These produce results that range within the specificity vs sensitivity space in such a way that type I and type II error are difficult to ascertain in real microbiome data when a single method is used. Recently, a consensus approach based on multiple differential abundance (DA) methods was recently suggested in order to increase robustness.

With dar, you can use dplyr-like pipeable sequences of DA methods and then apply different consensus strategies. In this way we can obtain more reliable results in a fast, consistent and reproducible way.

Installation

You can install the development version of dar from GitHub with:

# install.packages("devtools")
devtools::install_github("MicrobialGenomics-IrsicaixaOrg/dar")

Usage 

library(dar)
#> Registered S3 methods overwritten by 'vegan':
#>   method         from      
#>   reorder.hclust seriation 
#>   rev.hclust     dendextend
data("metaHIV_phy")

## Define recipe
rec <-
  recipe(metaHIV_phy, var_info = "RiskGroup2", tax_info = "Species") %>%
  step_subset_taxa(expr = 'Kingdom %in% c("Bacteria", "Archaea")') %>%
  step_filter_taxa(.f = "function(x) sum(x > 0) >= (0.03 * length(x))") %>%
  step_metagenomeseq(rm_zeros = 0.01) %>%
  step_maaslin()

rec
#> ── DAR Recipe ──────────────────────────────────────────────────────────────────
#> Inputs:
#> 
#>      ℹ phyloseq object with 451 taxa and 156 samples 
#>      ℹ variable of interes RiskGroup2 (class: character, levels: hts, msm, pwid) 
#>      ℹ taxonomic level Species 
#> 
#> Preporcessing steps:
#> 
#>      ◉ step_subset_taxa() id = subset_taxa__Suncake 
#>      ◉ step_filter_taxa() id = filter_taxa__Hot_water_crust_pastry 
#> 
#> DA steps:
#> 
#>      ◉ step_metagenomeseq() id = metagenomeseq__Crocetta_of_Caltanissetta 
#>      ◉ step_maaslin() id = maaslin__Tortita_negra

## Prep recipe
da_results <- prep(rec, parallel = TRUE)
da_results
#> ── DAR Results ─────────────────────────────────────────────────────────────────
#> Inputs:
#> 
#>      ℹ phyloseq object with 278 taxa and 156 samples 
#>      ℹ variable of interes RiskGroup2 (class: character, levels: hts, msm, pwid) 
#>      ℹ taxonomic level Species 
#> 
#> Results:
#> 
#>      ✔ metagenomeseq__Crocetta_of_Caltanissetta diff_taxa = 236 
#>      ✔ maaslin__Tortita_negra diff_taxa = 146 
#> 
#>      ℹ 124 taxa are present in all tested methods

## Consensus strategy
n_methods <- 2
da_results <- bake(da_results, count_cutoff = n_methods)
da_results
#> ── DAR Results ─────────────────────────────────────────────────────────────────
#> Inputs:
#> 
#>      ℹ phyloseq object with 278 taxa and 156 samples 
#>      ℹ variable of interes RiskGroup2 (class: character, levels: hts, msm, pwid) 
#>      ℹ taxonomic level Species 
#> 
#> Results:
#> 
#>      ✔ metagenomeseq__Crocetta_of_Caltanissetta diff_taxa = 236 
#>      ✔ maaslin__Tortita_negra diff_taxa = 146 
#> 
#>      ℹ 124 taxa are present in all tested methods 
#> 
#> Bakes:
#> 
#>      ◉ 1 -> count_cutoff: 2, weights: NULL, exclude: NULL, id: bake__Kürtőskalács

## Results
cool(da_results)
#> ℹ Bake for count_cutoff = 2
#> # A tibble: 124 × 2
#>    taxa_id taxa                   
#>    <chr>   <chr>                  
#>  1 Otu_63  Bacteroides_plebeius   
#>  2 Otu_216 Clostridium_sp_CAG_632 
#>  3 Otu_441 Brachyspira_sp_CAG_700 
#>  4 Otu_108 Prevotella_sp_CAG_520  
#>  5 Otu_257 Butyrivibrio_sp_CAG_318
#>  6 Otu_104 Prevotella_sp_CAG_1092 
#>  7 Otu_69  Bacteroides_sp_CAG_530 
#>  8 Otu_102 Prevotella_sp_AM42_24  
#>  9 Otu_159 Lactobacillus_ruminis  
#> 10 Otu_117 Alistipes_inops        
#> # ℹ 114 more rows

Contributing

Code of Conduct

Please note that the dar project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.