Collect mean quality by cycle. This tool generates a data table and chart of mean quality by cycle from a BAM file. It is intended to be used on a single lane or a read group's worth of data, but can be applied to merged BAMs if needed. This metric gives an overall snapshot of sequencing machine performance. For most types of sequencing data, the output is expected to show a slight reduction in overall base quality scores towards the end of each read. Spikes in quality within reads are not expected and may indicate that technical problems occurred during sequencing. Note: Metrics labeled as percentages are actually expressed as fractions!