PowerQuestion.R

library(tidyverse)
library("viridis")
n <- 100
sd <- 10

cutoffz_r <- qnorm(0.975) * (sd/sqrt(n))
cutoffz_l <- -cutoffz_r

min_ES <- 0.28
min_raw <- min_ES*sd

p <- pnorm(cutoffz_r, min_raw, sd/sqrt(n))
power <- 1-p

curves <- seq(3,6, by = 0.25)
colors <- viridis(length(curves))
curvesproto <- lapply(1:length(curves), function(x) stat_function(fun = dnorm,
                                                                  n = 101, args = list(mean = curves[x],
                                                                                       sd = sd/sqrt(n)), color = colors[x],
                                                                  alpha = 0.5))
curvesproto2 <- lapply(1:length(curves), function(x) stat_function(fun = dnorm, 
                                                                   args = list(mean = curves[x], sd = sd/sqrt(n)),
                                                                   xlim = c(cutoffz_r, min_raw),
                                                                   geom = "area",
                                                                   alpha = 0.2))

p1 <- ggplot(data = data.frame(x = c(-3, 10)), aes(x)) +
  stat_function(fun = dnorm, n = 101, args = list(mean = 0,
                                                  sd = sd/sqrt(n)),
                size = 1,
                color = "darkgrey") +
  ylab("") +
  scale_y_continuous(breaks = NULL) + 
  stat_function(fun = dnorm, n = 101,
                args = list(mean = min_raw, sd = sd/sqrt(n)),
                color = "black", size = 1) +
  geom_vline(xintercept = cutoffz_r, lty = 3, size = 1) +
  geom_vline(xintercept = min_raw, lty = 2, size = 1) +
  stat_function(fun = dnorm, 
                args = list(mean = min_raw, sd = sd/sqrt(n)),
                xlim = c(cutoffz_r,8),
                geom = "area",
                alpha = 0.2) +
  stat_function(fun = dnorm, 
                args = list(mean = min_raw, sd = sd/sqrt(n)),
                xlim = c(cutoffz_r, min_raw),
                geom = "area",
                alpha = 0.2) +
  theme_minimal() + xlab("Raw Effect")

p1 + curvesproto + curvesproto2