Dear All,

I am trying to use Shiny package from R. I have a user typed input and the code behind takes that input runs it across several databases and returns tables.(See the code attached below) What I need is instead of returning empty tables I should print an error message saying that an input is required. I havent accomplished that (tried validate and need) . Please also note that I am not in liberty to disclose all of the code written. Thank you for your time.

#################################### Server.R ##########################################

shinyServer(function(input, output) {
      datasetInput <- reactive({
    switch(input$dataset,
           "GSE1" = GSE1,
           "none" = null,
           'GSE2'=GSE2)
  })

      data <- reactive({ 
        validate(
          need(input$number != "", "Please enter an input here")
        )
      })

      qualC <- reactive({
        value=as.vector(input$checkGroup)
        value=sprintf('%s_%s.pdf',value,input$dataset)
        print(value)
               })


########################################    UI.R   ########################################

shinyUI(pageWithSidebar(
  # Application title
#
  headerPanel("Representation"),

  # Sidebar with controls to select a dataset and specify the number
  # of observations to view
  sidebarPanel(

   textInput("number", "Enter a gene:", value=""),
   actionButton("Gobutton", "Search"),

   selectInput("dataset", "Choose a dataset:", 
                choices = c('none', 'GSE1',"GSE2")),width=3
  ),

####################################### sessionInfo #############################################

R version 3.2.2 (2015-08-14)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252    LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                           LC_TIME=English_United States.1252

attached base packages:
 [1] grid      parallel  stats4    stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
 [1] Hmisc_3.17-0              Formula_1.2-1             survival_2.38-3           lattice_0.20-33
 [5] ggplot2_1.0.1             shiny_0.12.2              biomaRt_2.24.1            vsn_3.36.0
 [9] makecdfenv_1.44.0         affyio_1.36.0             BiocInstaller_1.18.4      affy_1.46.1
[13] targetscan.Hs.eg.db_0.6.1 RSQLite_1.0.0             DBI_0.3.1                 AnnotationDbi_1.30.1
[17] GenomeInfoDb_1.4.2        IRanges_2.2.7             S4Vectors_0.6.6           Biobase_2.28.0
[21] BiocGenerics_0.14.0

loaded via a namespace (and not attached):
 [1] reshape2_1.4.1        splines_3.2.2         colorspace_1.2-6      htmltools_0.2.6       XML_3.98-1.3
 [6] foreign_0.8-66        RColorBrewer_1.1-2    plyr_1.8.3            stringr_1.0.0         zlibbioc_1.14.0
[11] munsell_0.4.2         gtable_0.1.2          labeling_0.3          latticeExtra_0.6-26   httpuv_1.3.3
[16] preprocessCore_1.30.0 proto_0.3-10          Rcpp_0.12.1           acepack_1.3-3.3       xtable_1.7-4
[21] scales_0.3.0          limma_3.24.15         jsonlite_0.9.17       mime_0.4              gridExtra_2.0.0
[26] digest_0.6.8          stringi_0.5-5         tools_3.2.2           bitops_1.0-6          magrittr_1.5
[31] RCurl_1.95-4.7        cluster_2.0.3         MASS_7.3-44           R6_2.1.1              rpart_4.1-10
[36] nnet_7.3-11