server <- function(input, output) { output$params <- renderUI({ switch(input$dist, "Normal" = list( numericInput("mean", "Mean", value = 0), numericInput("sd", "Std Dev", value = 1, min = 0.1) ), "Binomial" = list( numericInput("size", "Trials", value = 10, min = 1), numericInput("prob", "Prob success", value = 0.5, min = 0, max = 1) ), "Poisson" = list( numericInput("lambda", "Lambda", value = 3, min = 0.1) ), "Exponential" = list( numericInput("rate", "Rate", value = 1, min = 0.1) )) })
if(dist == "Normal") { data <- rnorm(n, input$mean, input$sd) theory_curve <- function(x) dnorm(x, input$mean, input$sd) } else if(dist == "Binomial") { data <- rbinom(n, input$size, input$prob) theory_curve <- function(x) dbinom(x, input$size, input$prob) } else if(dist == "Poisson") { data <- rpois(n, input$lambda) theory_curve <- function(x) dpois(x, input$lambda) } else { data <- rexp(n, input$rate) theory_curve <- function(x) dexp(x, input$rate) } output) { output$params <
# Plot 1: theoretical PDF/PMF output$pdfPlot <- renderPlot({ if(dist %in% c("Binomial", "Poisson")) { x_vals <- 0:max(data) probs <- theory_curve(x_vals) df <- data.frame(x = x_vals, prob = probs) ggplot(df, aes(x, prob)) + geom_col(fill = "skyblue") + labs(title = "Theoretical Distribution", y = "Probability") } else { x_vals <- seq(min(data), max(data), length = 200) df <- data.frame(x = x_vals, density = theory_curve(x_vals)) ggplot(df, aes(x, density)) + geom_line(color = "blue", size = 1.2) + labs(title = "Theoretical PDF") } }) - renderUI({ switch(input$dist
shinyApp(ui, server) simulate_power <- function(dist = "norm", n = 30, effect_size = 0.5, alpha = 0.05, nsim = 1000) { # dist: "norm", "binom", "pois", "exp" # effect_size: Cohen's d for normal, odds ratio for binom, etc. pvals <- replicate(nsim, { if(dist == "norm") { x <- rnorm(n, mean = effect_size, sd = 1) y <- rnorm(n, mean = 0, sd = 1) t.test(x, y)$p.value } else if(dist == "binom") { x <- rbinom(n, 1, prob = 0.3 + effect_size) y <- rbinom(n, 1, prob = 0.3) prop.test(c(sum(x), sum(y)), c(n, n))$p.value } else if(dist == "pois") { x <- rpois(n, lambda = 5 + effect_size) y <- rpois(n, lambda = 5) t.test(x, y)$p.value } else if(dist == "exp") { x <- rexp(n, rate = 1/(1 + effect_size)) y <- rexp(n, rate = 1) wilcox.test(x, y)$p.value } }) "Normal" = list( numericInput("mean"
observeEvent(input$simulate, { # Generate data set.seed(123) dist <- input$dist n <- input$n
# Hypothesis test example (one-sample t-test) output$testResults <- renderPrint({ if(dist == "Normal") { t.test(data, mu = input$mean) # test against true mean -> should fail to reject } else { t.test(data, mu = mean(data)) # dummy example } }) }) }
# Plot 2: sampling distribution of the mean (simulated) output$samplingPlot <- renderPlot({ means <- replicate(1000, mean({ if(dist == "Normal") rnorm(n, input$mean, input$sd) else if(dist == "Binomial") rbinom(n, input$size, input$prob) else if(dist == "Poisson") rpois(n, input$lambda) else rexp(n, input$rate) })) df_means <- data.frame(mean = means) ggplot(df_means, aes(x = mean)) + geom_histogram(aes(y = after_stat(density)), bins = 30, fill = "orange", alpha = 0.6) + stat_function(fun = dnorm, args = list(mean = mean(means), sd = sd(means)), color = "red") + labs(title = "Sampling Distribution of the Mean (CLT in action)", x = "Sample mean") })