take a look here....
https://satijalab.org/seurat/cell_cycle_vignette.html#assign-cell-cycle-scores

Thanks orrzor :-) I did but the vignette doesn't really explain how the data from the gene sets is pulled together and how the scores are computed.

As we say in the vignette, the scores are computed using an algorithm developed by Itay Tirosh, when he was a postdoc in the Regev Lab (Science et al., 2016). The gene sets are also taken from his work.

You can read the methods section of https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4944528/ to see how the scoring works, but essentially- the method scores cells based on the expression of each gene in a signature set - after controlling for the expected expression of genes with similar abundance.

Does the Seurat object need to be normalized and scaled before applying cell cycle scoring? If not, would this function automatically do normalization/scaling?