Selective y variable in shiny plotly output - r

Question

I'm trying to include a plotly plot in a shiny app where the y variable is selected by the user. I initially used ggplot2 and plotly together, and the code I have works just fine for that. But because the number of data points is quite large, the plot takes several minutes to load, so I tried switching to plotly only because I read somewhere that that makes it faster. Unfortunately I cannot get the y variable selection to work.
I have tried the suggestions given here: Change plotly chart y variable based on selectInput and here: Error: invalid first argument with R Shiny plot and none of them work. At this point I have tried so many things I don't remember in detail, but basically I either get the error "invalid first argument" when using some variation of yvar <- get(input$yvariable1) and then including ~yvar in the plot function, or I get "Error: cannot set attribute on a symbol" when it's y = ~input$yvariable1. When I use y = newdata[ ,input$yvariable1] something gets plotted but it's completely wrong (the scale of the axis is up to 50k or something instead of 10 and the distribution is not right either - basically it looks nothing like when I plot it by simply entering the same y variable non-reactively).
My code looks as follows - in UI:
uiOutput("ySelection1")
in server:
function(input, output) {
output$ySelection1 <- renderUI({
varSelectInput("yvariable1", "Y Variable:", df[, c('PO_count_citing', 'cpc_3digits_count_citing', 'cpc_4digits_count_citing')], selected='PO_count_citing')
})
yvar1 <- eventReactive(input$yvariable1, {input$yvariable1})
output$plot1 <- renderPlotly({
newdata <- subset(df, Technology == input$type & appln_auth%in%input$PO)
validate(no_data(nrow(newdata)))
#yvar <- get(yvar1()) (failed attempt at making this work)
#yvar <- get(input$yvariable1) (another failed attempt)
scatterPlot <- plot_ly(newdata, x = ~appln_filing_year, y = ~input$yvariable1, type="scatter", mode="markers",
# Hover text:
text = ~paste(some text),
color = ~appln_auth)
})
}
But I can't get it to work. In the original ggplot2 version it was entered as aes(x = appln_filing_year, y = !!yvar1(), bla bla)
But the !! or even one ! or removing the brackets after yvar1 all throw up errors in plotly.
Does anyone have any suggestions?

Answer 1

Here is a simple example using get:
library(shiny)
library(plotly)
DF <- setNames(data.frame(rep(1:20, 5), mapply(runif, min = 1:5, max = 2:6, MoreArgs = list(n = 20))), c("x", paste0("y", 1:5)))
library(shiny)
ui <- fluidPage(
plotlyOutput("myPlot"),
selectInput("yvariable", "Select the Y variable", paste0("y", 1:5))
)
server <- function(input, output, session) {
output$myPlot <- renderPlotly({
req(input$yvariable)
plot_ly(data = DF, x = ~x, y = ~get(input$yvariable), type = "scatter", mode = "markers")
})
}
shinyApp(ui, server)