Source at gtools::stars.pval

format-pval.R

format_pval <- function(x, cut = 0.05) {
    x <- round(x, 3)
    x[x == 0] <- paste("<span style='color:red;'>&lt;", 0.001, "</span>")
    x[x < cut] <- paste0("<span style='color:red;'>", x[x < cut], "</span>")
    return(x)
}

stars-pval.R

stars_pval <- function(x) {
    unclass(symnum(x, corr = FALSE, na = FALSE, legend = FALSE,
                   cutpoints = c(0, 0.001, 0.01, 0.05, 0.1, 1),
                   symbols = c("***", "**", "*", ".", " ")))
}

Example:

stars_pval(c(0.5, 0.1, 0.05, 0.01, 0.001))
#> [1] " "   "."   "*"   "**"  "***"