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Advanced features

Handling multiple input files

Sometimes you have multiple input files that you want to merge for one sample. For example, a common use case is a single library that was spread across multiple sequencing lanes, yielding multiple input files that need to be merged and then run through the pipeline as one unit. Rather than putting multiple lines in your sample annotation sheet, which causes conceptual and analytical challenges, we introduce two ways to merge inputs:

  1. Use shell expansion characters (* or []) in your data_source definition or filename; for relatively simple merge cases this works well.
  2. Specify a merge table, which maps input files to samples for samples with more than one input file. To accommodate complex merger use cases, this is infinitely customizable.

To do the first option, simply change data source specification:

  data_R1: "${DATA}/{id}_S{nexseq_num}_L00*_R1_001.fastq.gz"
  data_R2: "${DATA}/{id}_S{nexseq_num}_L00*_R2_001.fastq.gz"

For the second option, provide in the metadata section of your project config file a path to merge table file:

  merge_table: mergetable.csv

Make sure the sample_name column of this table matches, and then include any columns needed to point to the data. Looper will automatically include all of these files as input passed to the pipelines.

Warning: do not use both of these options for the same sample at the same time; that will lead to multiple mergers.

Note: mergers are not the way to handle different functional/conceptual kinds of input files (e.g., read1 and read2 for a sample sequenced with a paired-end protocol). Such cases should be handled as separate derived columns in the main sample annotation sheet if they're different arguments to the pipeline.

Connecting to multiple pipelines

If you have a project that contains samples of different types, then you may need to specify multiple pipeline repositories to your project. Starting in version 0.5, looper can handle a priority list of pipelines. Starting with version 0.6, each path should be directly to a pipeline interface file.


  pipeline_interfaces: [pipeline_iface1.yaml, pipeline_iface2.yaml]

In this case, for a given sample, looper will first look in pipeline_iface1.yaml to see if an appropriate (i.e., protocol-matched) pipeline exists for this sample type. If one is found, looper will use that pipeline (or set of pipelines, as specified in the protocol_mapping). Once a pipeline is submitted any remaining interface files will be ignored. Until an appropriate pipeline is found, each interface file will be considered in succession. If no suitable pipeline is found in any interface, the sample will be skipped. In other words, the pipeline_interfaces value specifies a prioritized search list.