README.md

htseq-count-multi

htseq-count-multi is a modified version of htseq-count script that is part of HTSeq python package that allows multiple countings of the same .sam file in one pass.

Original htseq-count script allows counting of multiple .sam files at the same time, but does not allow performing multiple different types of countings on a single .sam file. This modified version allows arbitrary number of comparisons on single .sam input file.

How to run

Parameters for different counting types are provided as comma separated list. e.g. performing 3 counting jobs: 1) genes union gene_id 2) exon union gene_id 3) exon intersect strict gene_id

python htseq-count-multi.py \
                        -f sam \
                        --samout output.sam \
                        -t gene,exon,exon \
                        -i gene_id,gene_id,gene_id \
                        -m union,union,intersection-strict \
                        -c GF_counts.txt,EF_counts.txt,XF_counts.txt \
                        input.sam \
                        annotation.gtf

Counts are returned in separate text files.
Reads are returned as a single .sam file with each read containing new flags: GF:Z, [EF:Z, XF:Z, XG:Z, XH:Z, ...]

Parallel run

htseq-count runs as single thread job. To run it in multithread mode one can use GNU parallel

    samtools view -h -@ 20 input.bam \
        | parallel \
            -L 2 \
            -j 20 \
            --roundrobin \
            --header '(@.*\n)*' \
            --pipe python htseq-count-multi.py \
                        -f sam \
                        --samout output.{#}_temp.sam \
                        -t gene,exon,exon \
                        -i gene_id,gene_id,gene_id \
                        -m union,union,intersection-strict \
                        -c GF_counts.{#}_temp.txt,EF_counts.{#}_temp.txt,XF_counts.{#}_temp.txt \
                        input.sam \
                        annotation.gtf   

Files from individual jobs can be then merged together

# .sam files
samtools view -H input.bam \
        | cat - output.*_temp.sam \
        | samtools sort \
            -@ 20 \
            -n \
            -o output.bam
            
 # counts files
parallel -j 3 "awk -v 'OFS=\t' '
                                  {
                                        gene[\$1] += \$2
                                  }
                                  END {
                                         for (name in gene) {
                                            print name, gene[name] 
                                       }
                                  }' {1}_counts.*_temp.txt  \
                     | LC_COLLATE=C sort -k1,1 > {1}_counts.txt" ::: GF EF XF