Dấu hoa thị

df <- data.frame(group = c("A-B", "A-C", "B-C", "E-D", "E-F"),
                 pvalue = c(0.03, 0.62, 0.001, 0.0003, 0.05))

df
  group pvalue psign
1   A-B 0.0300     *
2   A-C 0.6200    ns
3   B-C 0.0010    **
4   E-D 0.0003   ***
5   E-F 0.0500    ns

df$psign <- ifelse(test = df$pvalue < 0.001,
                  yes = "***",
                  no = ifelse(test = df$pvalue < 0.01,
                              yes = "**",
                              no = ifelse(test = df$pvalue < 0.05,
                                          yes = "*",
                                          no = "ns")
                  ))

df
  group pvalue psign
1   A-B 0.0300     *
2   A-C 0.6200    ns
3   B-C 0.0010    **
4   E-D 0.0003   ***
5   E-F 0.0500    ns