Using reactive input within reactiveValue() function

Question

I am new to shiny and trying to figure out some reactive stuff.

Currently this works for a static csv.

## function to return random row from twitter csv
 tweetData <- read.csv('twitterData1.csv')


## stores reactive values 
appVals <- reactiveValues(
    tweet =  tweetData[sample(nrow(tweetData), 1), ],
    ratings = data.frame(tweet = character(), screen_name = character(), rating = character())
    )

I need the same block of reactive values to be funciton but using a selected csv using input$file.

appVals <- reactiveValues(
    csvName <- paste0('../path/', input$file),
    tweetData <- read.csv(csvName),
    tweet =  tweetData[sample(nrow(tweetData), 1), ],
    ratings = data.frame(tweet = character(), screen_name = character(), rating = character())
    )

I get the error:

Warning: Error in : Can't access reactive value 'file' outside of reactive consumer.

I've tried moving things around but I keep getting stuck, help appreciated!

Use = rather than <- in reactiveValues(). Those are names parameters, not variables. — MrFlick
– MrFlick, Commented Apr 12, 2021 at 4:17

Waldi · Accepted Answer · 2021-04-12 14:32:23Z

2

The error is telling that you should update the values inside a reactive expression.

First initialize the reactive values:

tweetData <- read.csv('twitterData1.csv')

appVals <- reactiveValues()
appVals$tweet <-  tweetData[sample(nrow(tweetData), 1), ]
appVals$ratings <- data.frame(tweet = character(), screen_name = character())

Then update them with a reactive:

observeEvent(input$file,{
    csvName <- paste0('../path/', input$file)
    if (file.exists(csvName) {
      tweetData <- read.csv(csvName)
      appVals$tweet =  tweetData[sample(nrow(tweetData), 1), ]
      appVals$ratings = data.frame(tweet = character(), screen_name = character(), rating = character())
     }
    })

edited Apr 12, 2021 at 14:32

answered Apr 12, 2021 at 5:29

Waldi

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2 Comments

mk2080 Over a year ago

thank you this is helpful! When I make this edit I now get the error that "Warning: Error in ..stacktraceon..: object 'appVals' not found". Is there something I need to do to initialize appVals in the code you recommend?

Waldi Over a year ago

see my edit with initial creation of the reactiveValues

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