Error in as.character: cannot coerce type 'closure' to vector of type 'character' [No stack trace available]

[anc2256]

UI.R

library(shiny)

shinyUI(pageWithSidebar(

headerPanel("UNC Dataverse Project Results "),

Getting User Inputs

sidebarPanel(

submitButton(text="Analyse")

),

mainPanel( tabsetPanel
(tabPanel("Result set 1",HTML("

Result Set1

"),plotOutput("Result1"),HTML),
tabPanel("Result Set 2",HTML("

Most used words associated with the hashtag

"),plotOutput("Result2"), HTML),
tabPanel("Result Set 3", plotOutput("Result3") ,HTML)

))

))

Server.R
setwd("C:/Users/achaudhari/Desktop/project")
sn <- read.csv("Admission_predict.csv", header=T)
UniversityDatabase <-function(sn)
{
require(plyr)
require(stringr)

output$Result1 <- table(sn$GRE.Score)
output$result2<- table(sn$University.Rating)
output$result3<-table(sn$Research)
return(output)
}

require(reshape)

#HISTOGRAM
output$Gre<- renderPlot({ hist(output$Gre,main="Histogram of Gre", xlab = "GRE") })
output$rating<- renderPlot({hist(output$rating,main="Histogram of Rating", xlab = "Rating") })
output$research<- renderPlot({hist(output$research, main="Histogram of esearch", xlab = "Research Institute") })

Error : Error in as.character: cannot coerce type 'closure' to vector of type 'character'
[No stack trace available

any suggestion or help