Add stars to p-value

Question

I have calculated the Anova F-Test p-value for differences in means for several variables. Now I would like to add "stars" that indicate the significance level of the p-value. I would like to have * for significance at at the 10% level, ** at the 5% level and *** at the 1% level.

My data looks like this:

structure(list(Variables = c("A", "B", "C", "D", "E"), 
               `Anova F-Test p-Value` = c(0.05, 5e-04, 0.5, 0.05, 0.01)), 
          class = "data.frame", row.names = c(NA, -5L))

Could someone help me with the code here?

Answer 1

You can build your own function. Note however that this is not the conventional star system (it's totally okay if you mention the scale somewhere though). See e.g. here.

stars.pval <- function(x){
  stars <- c("***", "**", "*", "n.s.")
  var <- c(0, 0.01, 0.05, 0.10, 1)
  i <- findInterval(x, var, left.open = T, rightmost.closed = T)
  stars[i]
}

transform(dat, stars = stars.pval(dat$`Anova F-Test p-Value`))

  Variables Anova.F.Test.p.Value stars
1         A                5e-02    **
2         B                5e-04   ***
3         C                5e-01  n.s.
4         D                5e-02    **
5         E                1e-02   ***