R Shiny Weierstrass Function

Simple R Shiny application demonstrating Weierstrass Function.

# © 2018 TheFlyingKeyboard and released under MIT License
# theflyingkeyboard.net
library(shiny)

f <- function(x, a = 0.5, b = 15, n = 200) {
  output = 0
  
  for(i in 0:n){
    output = output + (a ^ i) * cos((b ^ i) * i * x)
  }
  
  return(output)
}	

ui <- fluidPage(
  titlePanel("Weierstrass Function"),
   
  plotOutput("plot"),
   
  fluidPage(
    fluidRow(
      column(2, sliderInput("aSlider", "a:", min = 0.01, max = 0.99, value = 0.5)),
      column(2, numericInput("bInput", "b:", 13, min = 7, max = NA, step = 2, width = NULL)),
      column(2, numericInput("nInput", "iterations:", 10, min = 1, max = 200, step = NA, width = NULL)),
      column(2, textOutput("text"))
    )
  )
)

server <- function(input, output) {
   output$plot <- renderPlot({
      y = f(x = seq(2, 12, 0.01), a = input$aSlider, b = input$bInput, n = input$nInput)
      plot(seq(2, 12, 0.01), y, type = "l", col = "blue", xlab = "X")
      output$text <- renderText({paste("B must be >= ", (1 + (3 / 2) * pi) / input$aSlider)})
   })
}

shinyApp(ui = ui, server = server)