Shiny - Create reactive function from user string input

Question

I'm writing shiny app and I want to create mathematical functions from user input - There is textInput where user writes a function, e.g x^2, sin(x)+5 etc. Then, I want to plot this function so I have to concatenate string from textInput and 'function(x)' statement to get R function. As far as I know, I need to have reactive variable which contains the R function. I came up with that:

func<-reactive(
     bquote(function(x){ .(parse(text = input$fun)[[1]])}), quoted = TRUE
)

where input$fun is id of textInput. This solution doesn't work and I have no other idea.

NicE · Accepted Answer · 2015-03-01 10:36:39Z

2

You can use f<-function(x) {eval(parse(text=input$func))} to transform the input into a function.

Fron @JoeCheng:

While this certainly works, I'd caution anyone reading this to only use eval() on user input if the app will only be run locally. Apps that do this are not safe to deploy on a server because a user could feed in whatever code they want, for example system("rm -rf ~")

For example, in a shiny app:

app.R

library(shiny)

        ui <- shinyUI(fluidPage(
                mainPanel(textInput("func", "Function:", ""),
                          submitButton("Plot!"),
                          plotOutput("plot")
                          )
        ))
        server <- function(input, output, session) {
                output$plot<-renderPlot({
                        f<-function(x) {eval(parse(text=input$func))}
                        x<-1:10
                        plot(x,f(x))
                }                        
                )              
        }

shinyApp(ui = ui, server = server)

Would give you this: enter image description here

edited Mar 1, 2015 at 10:36

answered Mar 1, 2015 at 0:49

NicE

21.5k3 gold badges56 silver badges72 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Joe Cheng Over a year ago

While this certainly works, I'd caution anyone reading this to only use eval() on user input if the app will only be run locally. Apps that do this are not safe to deploy on a server because a user could feed in whatever code they want, for example system("rm -rf ~").

Sebastian Osiński Over a year ago

Yes, it works, but is there a way to create reactive function from that input? I want to plot it but also use it in other ways.

Collectives™ on Stack Overflow

Shiny - Create reactive function from user string input

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related