在闪亮的应用程序中返回绘图时返回无效的第一个参数错误

Question

Newbie user for Shiny so apologies if this is a silly question. I want to make an app version of a simulation function that I have already made. Here's the original function:

GeometricBrownian<-function(trials = 100, periods = 10, mean = .07, sd = .1, capital = 100)
{
  #Reads in the parameters
  paths <- trials
  count <- periods
  interval<- 5/count
  mean <- mean
  sigma <- sd
  sample <- capital
  
  #Generate matrix based on parameters
  sample<-matrix(0,nrow=(count+1),ncol=paths)
  
  #generates samples using GBM and inputted parameters
  for(i in 1:paths)
  {
    sample[1,i]<- capital
    for(j in 2:(count+1))
    {
      sample[j,i]<-sample[j-1,i]*exp(interval*(mean-((sigma)^2)/2)+((interval)^.5)*rnorm(1)*sigma) #Expression for Geometric Brownian Motion
    }
  } 
  
  #Plot the samples generated
  sample
  matplot(sample,main="Geometric Brownian",xlab="Periods",ylab="Total Value",type="l")
  
  #Reformat for summary results
  df<- as_tibble(sample)
  final <- na.trim(df[periods,1:trials])
  final <- as.data.frame(t(final))
  colnames(final) <- "Results"
  results <- as.numeric(final[,1])
  
  #Output a csv of trial results
  #write_csv(df, "All Trials Time Series.csv")
  
  #Print summary and histogram
  print(summary(final))
  print(
    ggplot(final, aes(x=Results))+
      geom_histogram(color = "white", 
                     alpha = .8, 
                     fill="lightblue",
                     bins = trials/(trials/10))+
      labs(title = "Trial Results", y = "Frequency")+
      theme_minimal()
  )
  
}

And now for my preliminary attempt at making it into a shiny app:

library(tidyquant)
library(shiny)
library(shinydashboard)

ui <- fluidPage(
  
  # App title ----
  headerPanel("Return Simulation"),
  
  # Sidebar panel for inputs ----
  sidebarPanel(
    numericInput("trials",
                 "Number of Trials:",
                 min = 10,
                 max = 10000,
                 step = 1,
                 value = 100),
    
    numericInput("periods",
                 "Number of Periods:",
                 min = 2,
                 max = 10000,
                 step = 1,
                 value = 10),
    
    numericInput("mean",
                 "Average Return (in decimals):",
                 min = -100,
                 max = 100,
                 step = .01,
                 value = .07),
    numericInput("sd",
                 "Return Standard Deviation (in decimals):",
                 min = -100,
                 max = 100,
                 step =.01,
                 value = .2),
    numericInput("capital",
                 "Starting Capital",
                 min = 0,
                 max = 100000,
                 value = 100),
    
  ),
  
  # Main panel for displaying outputs ----
  mainPanel(

    plotOutput("Plot")
  )
)
server <- function(input,output){
    Simulation<-function(trials = 100, periods = 10, mean = .07, sd = .1, capital = 100)
    {
      #Reads in the parameters
      paths <- trials
      count <- periods
      interval<- 5/count
      mean <- mean
      sigma <- sd
      sample <- capital
      
      #Generate matrix based on parameters
      sample<-matrix(0,nrow=(count+1),ncol=paths)
      
      #generates samples using GBM and inputted parameters
      for(i in 1:paths)
      {
        sample[1,i]<- capital
        for(j in 2:(count+1))
        {
          sample[j,i]<-sample[j-1,i]*exp(interval*(mean-((sigma)^2)/2)+((interval)^.5)*rnorm(1)*sigma) #Expression for Geometric Brownian Motion
        }
      } 
      
      #Return a tibble
      return(sample)
    }
    
    data <-reactive({Simulation(trials= input$trials,
                       periods = input$period,
                       mean =input$mean,
                       sd = input$sd,
                       capital = input$capital)
    })
    output$Plot <- renderPlot({
      matplot(data,main="Geometric Brownian",xlab="Periods",ylab="Total Value",type="l")

  })
  
}

shinyApp(ui,server)
runApp("~/shinyapp")

When I run the app, I get the following error:

Listening on http://127.0.0.1:4029
Warning: Error in <-: invalid first argument, must be vector (list or atomic)
  [No stack trace available]

My main question is, what am I doing wrong here? I suspect it's an issue with how I set up my reactive functions, but even after looking at examples, I'm having a hard time finding the mistake.

Answer 1

data() is a reactive function, you should call:

output$Plot <- renderPlot({
      matplot(data(),main="Geometric Brownian",xlab="Periods",ylab="Total Value",type="l")
})

and to avoid the NA error on input$period:

    data <-reactive({
                     req(!is.na(input$period))
                     Simulation(trials= input$trials,
                       periods = input$period,
                       mean =input$mean,
                       sd = input$sd,
                       capital = input$capital)
    })