Computes the Intraclass Correlation Coefficients ICC1, ICC2, ICC3, ICC1k, ICC2k, and ICC3k. Based on the development by Shrout1979, presentation by McGraw including errata corrections. Data is returned as presented in the form returned by the ICC function in the R package 'DescTools'. Shrout, Patrick E. and Fleiss, Joseph L. Intraclass correlations: uses in assessing rater reliability. Psychological Bulletin, 1979, 86, 420-3428. McGraw, Kenneth O. and Wong, S. P. (1996), Forming inferences about some intraclass correlation coefficients. Psychological Methods, 1, 30-46. and errata in Psychological Methods, 4, page 390.