[R] How to avoid endless loop in shiny

Greg Snow 538280 at gmail.com
Wed Mar 9 00:00:07 CET 2016

You need to use `isolate` on one of the assignments so that it does
not register as an update.  Here are a few lines of code from the
server.R file for an example that I use that has a slider for r
(correlation) and another slider for r^2 and whenever one is changed,
I want the other to update:

    updateSliderInput(session, 'r',

    updateSliderInput(session, 'r2', value=input$r^2)

I did end up in a loop once when I happened to choose just the wrong
value and the rounding caused a jumping back and forth, but all the
other times this has worked perfectly without the endless loop.

On Tue, Mar 8, 2016 at 12:35 PM, Michael Peng
<michael.gang.peng at gmail.com> wrote:
> Hi,
> I added two sliderInput into the app with package "shiny": sliderA and
> sliderB. The values in the two sliders are correlated. If I change sliderA,
> I used updateSliderInput to update the value in sliderB. And also If I
> change sliderB, I used  updateSliderInput to update the value in slideA.
> The problem is it is an endless loop. How can I use updateSliderInput
> without sending message to update the other slider.
> Thank.
>         [[alternative HTML version deleted]]
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Gregory (Greg) L. Snow Ph.D.
538280 at gmail.com

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