Unused Argument Error when trying to update reactiveVal - r

Question

I'm trying create a plot where I'm able to zoom in on a range and the y-axis rescales. Similar to Rescaling of y axis on an interactive plot depending on zoom except that I would like it to happen on double click.
library(shiny)
library(tidyverse)
ui <- fluidPage(
sidebarPanel(
actionButton('getdata', 'Get Data')
),
mainPanel(
plotOutput('plot', brush = brushOpts(id = 'brush'), dblclick = 'dclick')
)
)
server <- function(input, output, session) {
dat <- eventReactive(input$getdata, {
tibble('BusDate' = Sys.Date() - 0:10, 'Val' = rnorm(11))
})
dat2 <- reactive(dat())
observeEvent(input$dclick, {
brush <- input$brush
maxy <- brush$xmax
miny <- brush$xmin
if (is.null(miny)){
dat2(dat())
}else{
dat2(dat() %>% filter(BusDate > miny & BusDate < maxy))
}
}, ignoreInit = TRUE)
output$plot <- renderPlot({
ggplot(dat2(), aes(x = BusDate, y = Val)) + geom_line()
})
}
shinyApp(ui, server)
I keep getting an error that doesn't allow me to update dat2 within observe event.
Error in dat2: unused argument (dat() %>% filter(BusDate > miny & BusDate < maxy))
How do I update dat2 within observeEvent? I understand that its easier to update reactiveValues instead but I would like to know how it works specifically with reactiveVal

Answer 1

Try this:
library(shiny)
library(tidyverse)
ui <- fluidPage(
sidebarPanel(
actionButton('getdata', 'Get Data')
),
mainPanel(
plotOutput('plot', brush = brushOpts(id = 'brush'), dblclick = 'dclick')
)
)
server <- function(input, output, session) {
dat <- eventReactive(input$getdata, {
tibble('BusDate' = Sys.Date() - 0:10, 'Val' = rnorm(11))
})
dat2 <- reactiveVal()
observeEvent(input$dclick, {
brush <- input$brush
maxy <- brush$xmax
miny <- brush$xmin
if (is.null(miny)){
dat2(dat())
}else{
dat2(dat() %>% filter(BusDate > miny & BusDate < maxy))
}
}, ignoreInit = TRUE)
output$plot <- renderPlot({
df <- if(is.null(dat2())) dat() else dat2()
ggplot(df, aes(x = BusDate, y = Val)) + geom_line()
})
}
shinyApp(ui, server)
You are confusing reactive with reactiveVal. You can only update the value of reactive within its definition. Update with obj(xxx) is for reactiveVal.