These programs are all distributed free of charge. Please contact me with any problems you have with these programs whether it be bugs or built-in limitations.


A program that calculates a codon usage bias summary statistic, Nc'. It is based on the effective number of codons statistic Nc (or ENC) developed by Frank Wright, but improves upon it by accounting for background nucleotide composition. The package includes SeqCount, a companion program that prepares FASTA format files for use by ENCprime.

Platform/Description Size Download
Source code with Makefile (for Unix/Linux) 114k ENCprime.tar.gz Be sure to view the README file for installation notes.
Documentation 100k ENCprimedoc.pdf (The documentation is included in all the archives above).

Notes: The Unix version runs under Mac OSX. For Windows users, Anders Fuglsang has kindly provided a zip archive of ENCprime compiled on a Win32 XP system. Windows users can also try Fran Supek's Windows-based INCA package for codon usage analysis which computes ENCprime among other statistics. As a caution, neither program has been extensively tested by this author. Furthermore, Forrest Zhang has reported some problems with the Win32 version of SeqCount garbling sequence names (6/2/06).

Development Notes:

2/28/06 Anders Fuglsang found a bug in the calculation of the 3-fold average homozygozity when no 3-fold redundant codons are observed. In this case, the 3-fold average homozygosity is supposed to be estimated by taking the average of the 2-fold and 4-fold average homozygosities. The original code took the harmonic rather than arithmetic mean. The bug should have had only a small effect on datasets for which no 3-fold redudant codons were observed. The revised code contains comments showing the bug.

8/23/04 The documentation has been updated to address how ENCprime calculates Nc and Nc' when a small number of codons of any particular amino acid has been observed. The text helps explain why calculation of Nc by other programs may result in different values for short sequences. The basic reason is that different programs to compute Nc use different corrections for when there is insufficient data.

7/21/03 Multiple users have noticed SeqCount will crash with large files. This appears to happen during a calloc call within the program. The source of this bug is being investigated. For now, the crashing can be avoided by dividing large data files into smaller files and running them in batch.

1/20/03 Mike Cummings found a bug that caused SeqCount to crash when run with only a single sequence. The error had to do with how files were being closed, and has been fixed. A small bug was also fixed that caused ENCprime to crash under MacOSX.

1/8/03 Mike Cummings helped find a bug in the interactive mode of ENCprime. The genetic code setting would not change appropriately. This bug has been fixed.

9/11/02 Some small changes to the documentation were made.

9/3/02 A bug in SeqCount's calculation of the nucleotide composition was fixed.