How to change stats method from default ttest to Mann Whitney on ggplot

Question

I created this boxplot but need different stats method p values

using this code, namely the fucntion stat_compare_means BUt I would like to use mannwhitney/non-parametric p values instead as data is not normally distributed.

Also how can I see what options of stats methods there are to use? (help says use "method" within Stat_compare_means - I would like to be able to see a list of different methods that I can use for different tests in future

my_comparisons <- list (c("AA/AG","GG"))
  
  df <- GDFSNP1_for_R
  df  %>% 
    drop_na(Genotype) %>%
    pivot_longer(starts_with("GDF")) %>%
    mutate(name = factor(name, c("GDFb", "GDFt6", "GDFt12"))) %>%
    ggplot(. , aes(y = value, x = Genotype, group = Genotype, fill=Genotype)) + 
    facet_grid(~name, labeller = as_labeller(GDF_label)) + 
    geom_violin(width=0.9) +
    geom_boxplot(width=0.1, alpha=0.2) + 
    stat_compare_means(comparisons = my_comparisons)

Answer 1

Not sure where it's documented, but if you source ggpubr:::.method_info, you can get a look at the available methods.

{
    if (is.null(method)) 
        method = "wilcox.test"
    allowed.methods <- list(t = "t.test", t.test = "t.test", 
        student = "t.test", wiloxon = "wilcox.test", wilcox = "wilcox.test", 
        wilcox.test = "wilcox.test", anova = "anova", aov = "anova", 
        kruskal = "kruskal.test", kruskal.test = "kruskal.test")
    method.names <- list(t.test = "T-test", wilcox.test = "Wilcoxon", 
        anova = "Anova", kruskal.test = "Kruskal-Wallis")
    if (!(method %in% names(allowed.methods))) 
        stop("Non-supported method specified. Allowed methods are one of: ", 
            .collapse(allowed.methods, sep = ", "))
    method <- allowed.methods[[method]]
    method.name <- method.names[[method]]
    list(method = method, name = method.name)
}

It looks like the options for nonparametric methods are "wilcox.test" and "kruskal.test". I believe that Wilcox is the same thing as Mann-Whitney.