Shiny + ggplot: How to subset reactive data object?

Question

I am making a shiny app, that shows the user a ggplot after he selects the daterange he is interested in (= the range for the x-axis). So I guess I need to define a reactive data object (correct?).

The ggplot has some subsetting in it. R tells me that reactive data object is not subsettable. In my rookie understanding of ggplot, the subsetting has to be done inside the geom_bar(), geom_line() statements in order to obtain the graph that I want.

1. Can anyone suggest me how to proceed with the subsetting?

2. And how to reference the factor category in generating colors for the graph? Thanks!

   sample data

   A = c(3, 4, 3, 5)
   B = c(2, 2, 1, 4)
   Z = c(1, 2, 1, 2)
   R = c(-2, -1, -3, 0)
   S = c(7,7,7,9)
   mydata = data.frame(cbind(A,B,Z,R,S))
   dates = c("2014-01-01","2014-02-01","2014-03-01","2014-04-01")
   mydata$date = as.Date(dates)
   mydata.m = melt(mydata,id="date")
   names(mydata.m) = c("variable", "category","value")
   

   shiny server: select observations as per user input (dateRangeInput)

   data.r = reactive({
     a = subset(mydata.m, variable %in% input$daterange)
     return(a)
   })
   

   shiny server: make the plot

   output$myplot = renderPlot({
   
     # ggplot with proper reference to reactive function <<data.r()>>
     s = ggplot(data.r(), aes(x=variable, fill=category)) +   
   
       # bars for categories A, B, Z: needs subsetting the data... but how?
       + geom_bar(data=subset(data.r(), category %in% c("A","B")), aes(y=value), stat="identity", position="stack")
       + geom_bar(subset=.(category=="Z"), aes(y=-value), stat="identity")
   
       # lines for categories R, S: same.
       + geom_line(subset=.(category=="R"), aes(y=value)) 
       + geom_line(subset=.(category=="S"), aes(y=value))
   
       # how to reference the factor <<category>> in reactive function <<data.r()>>?
       + scale_fill_manual(breaks = levels(category), values = mycolorgenerator(length(levels(category))))
   
     print(s)
   
   })
   

UI.R

# INPUT PART

library(shiny)

shinyUI(pageWithSidebar(
  # Application title
  headerPanel("My App"),

  sidebarPanel( 

    dateRangeInput("daterange", "Date range:",
               start  = "2014-01-01",
               end    = "2014-04-01",
               min    = "2014-01-01",
               max    = "2014-04-01",
               format = "dd/mm/yyyy",
               separator = "-"),

    submitButton(text="Update!")
  ),
# -----------------------------------------------

# OUTPUT PART

  mainPanel(
    tabsetPanel(
      tabPanel("Tab 1", h4("Head 1"),plotOutput("myplot"))
    )
  )
))

SERVER.R

library(reshape)
library(shiny)
library(ggplot2)



# GEN DATA -----------------------------------------------

A = c(3, 4, 3, 5)
B = c(2, 2, 1, 4)
Z = c(1, 2, 1, 2)
R = c(-2, -1, -3, 0)
S = c(7,7,7,9)
mydata = data.frame(cbind(A,B,Z,R,S))
dates = c("2014-01-01","2014-02-01","2014-03-01","2014-04-01")
mydata$date = as.Date(dates)
mydata.m = melt(mydata,id="date")
names(mydata.m) = c("variable", "category","value")







# SERVER -----------------------------------------------
shinyServer(function (input, output) {


# DATA

data.r = reactive({
  a = subset(mydata.m, variable %in% input$daterange)
  return(a)
})



# GGPLOT

mycolorgenerator = colorRampPalette(c('sienna','light grey')) 


output$myplot = renderPlot({

  # ggplot with proper reference to reactive function <<data.r()>>
  s = ggplot(data.r(), aes(x=variable, fill=category))  +  

    # bars for categories A, B, Z: needs subsetting the data... but how?
     geom_bar(data=subset(data.r(), category %in% c("A","B")), aes(y=value), stat="identity", position="stack") +
     geom_bar(subset=.(category=="Z"), aes(y=-value), stat="identity") +

    # lines for categories R, S: same.
     geom_line(subset=.(category=="R"), aes(y=value)) +
     geom_line(subset=.(category=="S"), aes(y=value)) +

    # how to reference the factor <<category>> in reactive function <<data.r()>>?
     scale_fill_manual(breaks = levels(category), values = mycolorgenerator(length(levels(category))))

  print(s)


})
})

Answer 1

(The complete server.R and ui.R really helped)

I'm not sure where you got the .() function from or the idea that geom_bar has a subset= parameter. But here's an updated renderPlot that doesn't seem to generate any errors at least

output$myplot = renderPlot({

  dd<-data.r()
  # ggplot with proper reference to reactive function <<data.r()>>
  s = ggplot(dd, aes(x=variable, fill=category))  +  

    # bars for categories A, B, Z: needs subsetting the data... but how?
     geom_bar(data=subset(dd, category %in% c("A","B")), aes(y=value), 
         stat="identity", position="stack") +
     geom_bar(data=subset(dd, category=="Z"), aes(y=-value), stat="identity") +

    # lines for categories R, S: same.
     geom_line(data=subset(dd, category=="R"), aes(y=value)) +
     geom_line(data=subset(dd, category=="S"), aes(y=value)) +

     scale_fill_manual(breaks = levels(dd$category), 
         values = mycolorgenerator(length(levels(dd$category))))

  print(s)
})

Mostly I changed the data= to explicit subset() calls