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Get read coverages from BAM file

Source: R/model_decay.R
get_coverage.Rd

Get the read coverages for each transcript in the BAM file (or a GAlignments object). The read coverages are sampled at 100 positions along the transcript, and the coverage is scaled by dividing the coverage at each position by the total read counts for the transcript. If a BAM file is provided, alignment with MAPQ < 5, secondary alignments and supplementary alignments are filtered out. A GAlignments object can also be provided in case alternative filtering is desired.

Usage

get_coverage(bam, min_counts = 10, remove_UTR = FALSE, annotation)

Arguments

bam

path to the BAM file, or a parsed GAlignments object

min_counts

numeric, the minimum number of alignments required for a transcript to be included

remove_UTR

logical, if TRUE, remove the UTRs from the coverage

annotation

(Required if remove_UTR = TRUE) path to the GTF annotation file

Value

a tibble of the transcript information and coverages, with the following columns:

  • transcript: the transcript name / ID

  • read_counts: the total number of aligments for the transcript

  • coverage_1-100: the coverage at each of the 100 positions along the transcript

  • tr_length: the length of the transcript

Examples

ppl <- example_pipeline("BulkPipeline")
#> Writing configuration parameters to:  /tmp/RtmpgpEV0i/file25bfed204dd/config_file_9663.json 
#> Configured steps: 
#> 	genome_alignment: TRUE
#> 	isoform_identification: TRUE
#> 	read_realignment: TRUE
#> 	transcript_quantification: TRUE
#> samtools not found, will use Rsamtools package instead
ppl@steps["isoform_identification"] <- FALSE
ppl <- run_step(ppl, "read_realignment")
#> Running step: read_realignment
#> Using reference annotation for transcriptome assembly.
#> Import genomic features from the file as a GRanges object ... 
#> OK
#> Prepare the 'metadata' data frame ... 
#> OK
#> Make the TxDb object ... 
#> Warning: The "phase" metadata column contains non-NA values for features of type
#>   stop_codon. This information was ignored.
#> Warning: genome version information is not available for this TxDb object
#> OK
#> Realigning sample sample1 -> /tmp/RtmpgpEV0i/file25bfed204dd/sample1_realign2transcript.bam
#> Warning: samtools not found, using Rsamtools instead, this could be slower and might fail for large BAM files.
#> Skipped sorting BAM files.
#> Realigning sample sample2 -> /tmp/RtmpgpEV0i/file25bfed204dd/sample2_realign2transcript.bam
#> Warning: samtools not found, using Rsamtools instead, this could be slower and might fail for large BAM files.
#> Skipped sorting BAM files.
#> Realigning sample sample3 -> /tmp/RtmpgpEV0i/file25bfed204dd/sample3_realign2transcript.bam
#> Warning: samtools not found, using Rsamtools instead, this could be slower and might fail for large BAM files.
#> Skipped sorting BAM files.
x <- get_coverage(ppl@transcriptome_bam[[1]])
head(x)
#> # A tibble: 1 × 103
#>   transcript   coverage_1 coverage_2 coverage_3 coverage_4 coverage_5 coverage_6
#>   <chr>             <dbl>      <dbl>      <dbl>      <dbl>      <dbl>      <dbl>
#> 1 ENSMUST0000…      0.880          1          1          1          1          1
#> # ℹ 96 more variables: coverage_7 <dbl>, coverage_8 <dbl>, coverage_9 <dbl>,
#> #   coverage_10 <dbl>, coverage_11 <dbl>, coverage_12 <dbl>, coverage_13 <dbl>,
#> #   coverage_14 <dbl>, coverage_15 <dbl>, coverage_16 <dbl>, coverage_17 <dbl>,
#> #   coverage_18 <dbl>, coverage_19 <dbl>, coverage_20 <dbl>, coverage_21 <dbl>,
#> #   coverage_22 <dbl>, coverage_23 <dbl>, coverage_24 <dbl>, coverage_25 <dbl>,
#> #   coverage_26 <dbl>, coverage_27 <dbl>, coverage_28 <dbl>, coverage_29 <dbl>,
#> #   coverage_30 <dbl>, coverage_31 <dbl>, coverage_32 <dbl>, …