plot_beta.R

plot_beta <- function(mean_1 = 0, mean_2 = 1,
                      sd_1 = 1, sd_2 = 1,
                      fill_alpha = "red",
                      fill_beta = "green",
                      alpha = .05, zend = 3,
                      title = ""){
  # plots alpha error and beta error in two normal curves
  # arguments:
  # mean_1, mean_2: mean values of normal curves
  # sd_1, sd_2: sds of normal curves
  # fill_alpha, fill_beta: fill color for alpha and beta error
  # zend: end value (as z value) for alpha error shaded area




  library(ggplot2)
  library(cowplot)


  zkrit <- qnorm(1 - alpha)


  # from 3sd left to 3sd right to the mean
  x_1 <- seq(from = mean_1 - 3 * sd_1, to = mean_1 + 3*sd_1, by = .01)
  MyDF_1 <- data.frame(x = x_1, y = dnorm(x_1, mean = mean_1, sd = sd_1))


  x_2 <- seq(from = mean_2 - 3 * sd_2, to = mean_2 + 3*sd_2, by = .01)
  MyDF_2 <- data.frame(x = x_2, y = dnorm(x_2, mean = mean_2, sd = sd_2))


  MyDF_1_subset <- subset(MyDF_1,
                x >= mean_1 + zkrit * sd_1 & x < mean_1 +
                  zend * sd_1)

  MyDF_2_subset <- subset(MyDF_2,
                x >= mean_1 - zend * sd_1 & x < mean_1 +
                  zkrit * sd_1)



  p1 <- ggplot(MyDF_1, aes(x = x, y = y)) + geom_line() +
    geom_area(data =  MyDF_1_subset,
              aes(y = y), fill = fill_alpha, color = NA, alpha = .5) +
    ylab("") + xlab("") +
    geom_line(data =  MyDF_2, aes(x = x, y = y)) +
    geom_area(data =  MyDF_2_subset,
              aes(y = y), fill = fill_beta, color = NA, alpha = .5) +
    ggtitle(title)

  print(p1)


}

#debug(plot_beta)
plot_beta(sd_1 = 0.4,
          sd_2 = 0.4)


plot_beta(sd_1 = 0.6,
          sd_2 = 0.6)