The aim of this plot is to justify the use of Spearman's instead of Pearson's, because, analysing summary stats of variables ad QQplots I noticed that there aren't gaussian distributions of values. And for that reason Spearman's is a more robust indicator of correlation . Maybe I can demonstrate that by plotting columns of ranks instead column of variables ? like they said here : plotting spearman correlation (with geom_smooth?) - #3 by Matthias