bam files not sorted by samtools sort

[Dipro]

Hi,

Could I please be adviced on the following problem. I have sam files generated from bismark. I converted it to bam file using samtools view and sorted it by coordinates using samtools sort. When I checked the header of both the sorted and unsorted bam files, they both stated the files are unsorted.

I am unsure why this would be the case.

Would anyone be able to shed light on this issue?

Thanks

[maubp]

Which version of samtools did you use? Older versions never bothered to update the header (but still sorted the reads).

[Dipro]

I am using version 0.1.18. I am now certain that the files had not been sorted. I ran the files through our downstream analysis programs which threw an error indicating the flies were unsorted.

[maubp]

The best test if a BAM file is sorted is to try "samtools index your_file.bam", if that works the file is coordinate sorted.