Subseting a dataframe by column names does not respond when applied in a shiny app

Question

I have a simple shiny app in which I subset a dataframe by row selection and by column names selection. After subseting by rows I tried 3 different methods to subset it by columns as well but the dataframe remains the same. More specifically I have used :

keeps <- c("Database","Organism",input$sta)
    #a[, (colnames(a) %in% input$sta)]
    #a[keeps]
    a[ , which(names(a) %in% keeps)]

but nothing seems to work

#data
Database<-c("Composite","DB","TC","RH","DGI","DCH","DCH","DCH","LDP")
Organism<-c("Human","Human","Human","Human","Human","Human","Mouse","Rat","Human")
Unique_Drugs<-c(12672,5130,1425,3090,6100,2019,250,736,1182)
Unique_Targets<-c(3987,2175,842,2308,2413,1441,198,327,702)
Mean_S.D.Targets_per_Drug<-c("5.87 ± 6.72","2.60 ± 6.87","2.28 ± 3.76","3.29 ± 5.03","3.60 ± 5.21","6.28 ± 14.29"
                             ,"1.92 ± 1.83"
                             ,"4.11 ± 5.32"
                             ,"4.27 ± 8.25"
)
Mean_S.D.Drugs_per_Target<-c("11.63 ± 15.59",
                             "12.52 ± 23.93",
                             "10.71 ± 8.37",
                             "12.98 ± 17.57",
                             "23.44 ± 25.65",
                             "13.87 ± 34.23",
                             "8.20 ± 18.44",
                             "14.82 ± 9.36",
                             "17.43 ± 9.34"
)
Unique_Drug_Target_Associations<-c(
45276,
14598,
3599,
12439,
23048,
13872,
594,
2876,
3915)

db<-data.frame(Database,Organism,Unique_Drugs,Unique_Targets,Mean_S.D.Drugs_per_Target,Mean_S.D.Targets_per_Drug, Unique_Drug_Target_Associations)


#ui.r
library(shiny)
library(shinydashboard)
library(DT)
ui <- dashboardPage(
  dashboardHeader(
    title = "Stats Table"
  ),
  dashboardSidebar(
    uiOutput("dbase"),
    tags$hr(),
    uiOutput("stats")



  ),
  dashboardBody(
    DTOutput('tbl')
  )
)
#server.r
library(shiny)
library(shinydashboard)
library(DT)
server <- function(input, output,session) { 
  output$dbase<-renderUI({
    checkboxGroupInput("base", label = "Specify dataset(s)",
                 choices = list("Composite","DB","TC","RH","DGI","DCH","LDP"),
                 selected = c("Composite","DB","TC","RH","DGI","DCH","LDP")
    )
  })
  output$stats<-renderUI({
    checkboxGroupInput("sta", label = "Specify statistic(s)",
                       choices = list("# Unique Drugs"="Unique_Drugs",
                                      "# Unique Targets"="Unique_Targets",
                                      "# Unique Drug-Target Associations"="Unique_Drug_Target_Associations",
                                      "# of Targets per Drug"="Mean_S.D.Targets_per_Drug",
                                      "# of Drugs per Target"="Mean_S.D.Drugs_per_Target"
                       ),
                       selected = c("Unique_Drugs","Unique_Targets","Unique_Drug_Target_Associations","Mean_S.D.Targets_per_Drug","Mean_S.D.Drugs_per_Target")
    )
  })

  df_subset <- reactive({
    a <- subset(db, Database %in% input$base)
    keeps <- c("Database","Organism",input$sta)
    #a[, (colnames(a) %in% input$sta)]
    #a[keeps]
    a[ , which(names(a) %in% keeps)]
    return(a)
  })

  output$tbl = renderDT(
    df_subset(), options = list(lengthChange = FALSE)
  )
  }

Answer 1

You were quite close. The first problem is that in your definition of df_subset, you use a which is not defined anywhere else in the script. I guess you meant to use db there instead of a. The second problem is that when you subset a, you do not assign it again to a, and so when you return a it will not be the subsetted version. Below is the fixed version of df_subset.

df_subset <- reactive({

  # I stuck to the uncommented version of your subset, but I guess the others will work too
  keeps <- c("Database","Organism",input$sta)

  # assigning the subset of db to tmp
  tmp <- db[ , which(names(db) %in% keeps)]

  # returning tmp
  return(tmp)
})