I have reactive data frame in the server.R program. I want to update the columns of the data frame. In the code below the attempt to perform str_trim on a column of the data frame throws the error:
Error in <-: invalid (NULL) left side of assignment
If I leave the str_trim line out the code below works fine.
server <- function(input, output, session) {
observeEvent(input$gobutton, {
TD <- odbcConnect(dsn="yyyy", uid="xxxxx", pwd=rstudioapi::askForPassword())
DB_Table <- paste0(input$DB,".",input$TableName)
Sql <- paste0("select ColumnName, ColumnType from DBC.ColumnsV where databaseName ='",input$DB,"' and tableName = '",input$TableName,"'")
ColNames <- reactive({sqlQuery(TD, Sql)})
Int_Cols <- reactive({ColNames() %>% filter(ColumnType %in% c("I ","I1") & ColumnName != "Emp_ID") })
This line produces the error.
Int_Cols()$ColumnName <- reactive({str_trim(Int_Cols()$ColumnName)})
shiny output
output$OutputMessage <- renderText({paste("QC results")})
output$QCresults <- renderTable({Int_Cols()})
})
}
I don't quite understand how to work with reactive objects or when they are needed in a shiny app. Can anyone point to a source of info on the 'reactive' concept?