How can I display time series graph with its forecasting line? - r

Question

The object is gettig parameters from users to make them understand the forecasting techniques. Therefore, i would like to begin with moving average. Eventhough the work is quite simple, i couldnt manage and i have some issues.
One error occurs: ERROR: missing value where TRUE/FALSE needed.
I do not understand why do I get this?
I want to show forecasted values for next period. But with this ready formula does not provide that?
`
library(shiny)
shinyUI(pageWithSidebar(
headerPanel("Forecasting Methods"),
sidebarPanel(
h3(strong("Moving Average",style = "color:black")),
br(),
sliderInput("ord","Order Size:",min = 1, max = 100, step= 1, value = 15),
),
mainPanel(
plotOutput(outputId = "ma1", width = "700px",height = "400px"))
))
library(shiny)
library(ggplot2)
library(forecast)
library(TTR)
shinyServer(function(input, output){
output$ma1 <- renderPlot(
tmp <- data.frame(time = 1:100, sales = round(runif(100, 150, 879))),
sm <- SMA(tmp[,"sales"],order=input$ord),
y <-ggplot(tmp, aes(time, sales)) + geom_line() + geom_line(aes(time,sm),color="red") + xlab("Days") + ylab("Sales Quantity")+ ggtitle("Moving Average"),
y
)
})

Answer 1

How is this:
library(shiny)
library(ggplot2)
library(forecast)
library(TTR)
ui <- pageWithSidebar(
headerPanel("Forecasting Methods"),
sidebarPanel(
h3(strong("Moving Average",style = "color:black")),
br(),
sliderInput("ord","Order Size:",min = 1, max = 100, step= 1, value = 15)
),
mainPanel(
plotOutput(outputId = "ma1", width = "700px",height = "400px"))
)
server <- function(input, output){
n <- 0
output$ma1 <- renderPlot({
input$ord
tmp <- data.frame(time = 1:100, sales = round(runif(100, 150, 879)) )
sm <- SMA(tmp[,"sales"],order=input$ord)
title <- sprintf("Moving Average (%d)",n)
n <<- n+1
y <-ggplot(tmp, aes(time, sales)) +
geom_line() +
geom_line(aes(time,sm),color="red") +
xlab("Days") + ylab("Sales Quantity")+ ggtitle(title)
y
})
}
shinyApp(ui, server)
Yielding:
As to your program - I could not reproduce your errors exactly:
1 - the program as posted would not run. The server function code block was not enclosed in curly brackets ({}), but was structured like the ui function code (comma separated statements). This is wrong. The ui function code not a function like the server code, rather it series of function calls that output html/css/javascript. Try them from the R-console to see what I mean.
2 - the UI function had at least one extraneous comma that I had to get rid of in order for it to work.
3 - using input$ord in the output$ma1 code that initializes the sm dataframe was not enough to cause the function to be reactive, and be triggered on every update of the slider. Not sure why that was not enough, but when I added another instance of input$ord to the front of the function it worked.
4- I also put a counter in the title of the output$ma1 to help me debug the above-debugged lack of reactivity.
5 - I also combined both the shiny ui.R and server.R files into one file as this example is small and makes it easy to see everything at once. Note that it can be hard matching ui.R and server.R code with the Rstudio tabbed editor - it is worth getting another editor (like Atom or Notepad++) to help code if you need more than one file.