vignettes

[svteichman]

Several vignettes:

• running fastEmuFit() with user-chosen small reference set or default data-driven reference set (note that this could be run with phyloseq or TreeSummarized Experiment object and point user to appropriate radEmu vignettes, note that it can be run with clustered data and point user to appropriate `radEmu vignette
• running fastEmuFit() with sample splitting or thinning to choose reference set (although this could just be a note in the above vignette)
• running fastEmuFit() to run score tests in parallel

[svteichman]

currently vignette exists to run with data-driven reference set