Changes in version 1.2.0 (2025-01-16)                  

    o   Update reference database to GTDB release 220.

    o   For GTDB release 220, map_taxa() maps from old to new names identified in
	post-curation cycle
	(https://data.gtdb.ecogenomic.org/releases/release220/220.0/RELEASE_NOTES.txt).

    o   Add get_metric_byrank() to return chemical metric for all taxa at a given
	rank, calculated by aggregating abundance-weighted amino acid compositions.

    o   Add `drop.groups` argument to read_RDP() with default of FALSE.
	Classification to non-prokaryotic groups was an issue with previous
	reference databases but not the GTDB, and dropping root- and domain-
	level classifications may lose information.

    o   Add 'rootrank' (Root) taxon to RefDB/GTDB_220/taxon_AA.csv.xz to permit
	complete mapping of RDP output with GTDB reference database.

    o   Elemental formulas (O2 and H2O) are no longer subscripted in documentation.

                 Changes in version 1.1.0 (2024-07-01)                  

    o   Change default reference database to GTDB version 214.

    o   Normalize file names in RefDB/RefSeq_206 and RefDB/GTDB_214 for easier
	programmatic access.

    o   Add 'xvar' and 'yvar' arguments to plot_metrics().

    o   Add 'Domain' as an allowed rank in ps_taxacounts().

    o   Move calc_metrics() and add_hull() to the canprot package, which is now
	imported by chem16S.

    o   A single 'metrics' argument replaces 'x' and 'y' in plot_ps_metrics2().

                 Changes in version 1.0.0 (2023-07-17)                  

    o   Add functions for integration with phyloseq: ps_taxacounts(), ps_metrics(),
	plot_ps_metrics(), and plot_ps_metrics2().

    o   Add vignettes: *Chemical metrics of reference proteomes*, *Integration of
	chem16S with phyloseq*, and *Plotting two chemical metrics*.

    o   Change default reference database from RefSeq to GTDB.

    o   Add metrics: nO2, GRAVY, pI, MW, length, H/C, N/C, O/C, and S/C.

    o   Rename readRDP() to read_RDP(), getmetrics() to get_metrics(), plotmet() to
	plot_metrics(), and other analogous changes to function names.

    o   First release on CRAN.

                        Changes in version 0.1.3                        

    o   Add 'pt.open.col' argument to plotmet() for border color of open plot symbols.

    o   Add 'xlab' and 'ylab' arguments to plotmet().

                        Changes in version 0.1.2                        

    o   Add reference proteomes for taxa based on the Genome Taxonomy Database (GTDB).

    o   Add 'return_AA' argument to getmetrics() to return amino acid composition.

    o   Add 'zero_AA' argument to getmetrics() to specify amino acids with
	abundances set to zero for calculating chemical metrics.

                        Changes in version 0.1.1                        

    o   Add 'cex' argument to plotmet().

    o   Don't drop dimensions in readRDP().

    o   Change "estimated community proteomes" to "community reference proteomes".

                        Changes in version 0.1.0                        

    o   First release on GitHub.