polarHistogram builds many histogram and arranges them around a circle to save space.

C. Ladroue, after Kettunen, J. et al. Genome-wide association study identifies multiple loci influencing human serum metabolite levels. Nat Genet advance online publication (2012). URL http://dx.doi.org/10.1038/ng.1073.

CC licence: http://creativecommons.org/licenses/by-nc-sa/3.0/

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v. 21022012

The data frame is expected to have at least four columns: family, item, score and value.

The three first columns are categorical variables, the fourth column contains non-negative values.

See testPolarHistogram.R for an example.

Each bar represents the proportion of scores for one item. Items can be grouped by families.

The resulting graph can be busy and might be better off saved as a pdf, with ggsave("myGraph.pdf").