Introduction

This document describes the output produced by the pipeline. Most of the plots are taken from the MultiQC report, which summarises results at the end of the pipeline.

The directories listed below will be created in the results directory after the pipeline has finished. All paths are relative to the top-level results directory.

Pipeline overview

The pipeline is built using Nextflow and processes data using the following steps:

  • VCF index - Create index of input VCF/gVCF files
  • VCF processing - Process VCF/gVCF files to analyse SNP density, InDel sizes, per-base nucleotide diversity, ROH, heterozygosity, and allele frequency
  • VCF stats - Parses VCF/gVCF files, produce text file stats and plot in a PDF file
  • MultiQC - Aggregate report describing results and QC from the whole pipeline
  • Pipeline information - Report metrics generated during the workflow execution

VCF index

Use Bgzip to generate index

Output files
  • Index in tbi format: <filename>.tbi

VCF processing

Output files
  • Single nucleotide polymorphisms (SNP) density calculated by VCFtools: <filename>.snpden.
  • Insertion or deletion (InDel) sizes calculated by VCFtools, output a histogram file: <filename>.indel.hist.
  • Per-site (per-base) nucleotide diversity calculated by VCFtools (output compressed): <filename>.sites.pi.gz.
  • Index for per-site nucleotide diversity file: <filename>.sites.pi.gz.tbi.
  • Runs of homozygosity (ROH) generated by BCFtools: <filename>.roh.
  • Heterozygosity generated by VCFtools: <filename>.het.
  • Allele frequency calculated by VCFtools: <filename>.frq.

VCF stats

Output files
  • Summary statistics generated by BCFtools(output compressed): <filename>.bcftools_stats.txt.gz.
  • Plots generated by plot_vcfstats
    • Combined PDF report: <filename>.plot-vcfstats.pdf.
    • Individual plot files and supporting data, archived and compressed by tar: <filename>.plot-vcfstats.tar.gz.

MultiQC

Output files
  • multiqc/
    • multiqc_report.html: a standalone HTML file that can be viewed in your web browser.
    • multiqc_data/: directory containing parsed statistics from the different tools used in the pipeline.
    • multiqc_plots/: directory containing static images from the report in various formats.

MultiQC is a visualization tool that generates a single HTML report summarising all samples in your project. Most of the pipeline QC results are visualised in the report and further statistics are available in the report data directory.

Results generated by MultiQC collate pipeline QC from supported tools e.g. FastQC. The pipeline has special steps which also allow the software versions to be reported in the MultiQC output for future traceability. For more information about how to use MultiQC reports, see http://multiqc.info.

Pipeline information

Output files
  • pipeline_info/
    • Reports generated by Nextflow: execution_report.html, execution_timeline.html, execution_trace.txt and pipeline_dag.dot/pipeline_dag.svg.
    • Reports generated by the pipeline: pipeline_report.html, pipeline_report.txt and software_versions.yml. The pipeline_report* files will only be present if the --email / --email_on_fail parameter's are used when running the pipeline.
    • Reformatted samplesheet files used as input to the pipeline: samplesheet.valid.csv.
    • Parameters used by the pipeline run: params.json.

Nextflow provides excellent functionality for generating various reports relevant to the running and execution of the pipeline. This will allow you to troubleshoot errors with the running of the pipeline, and also provide you with other information such as launch commands, run times and resource usage.