Dynamic Pie Chart in R Using A Shiny Dashboard - r

Question

I am currently working on a Shiny dashboard that has a slider that outputs the optimal portfolio weights of stocks, gold and silver for a given volatility value using the slider input. I have been able to output the values with a dynamic text output given the slider input, but I cannot figure out how to turn these values into a graph as the text output in Shiny seems to require a function. How can I add a pie chart to this code using the values I get from slidervalues()? It outputs a list of 5 numerical values, now I want to chart the first 3 of them in a pie chart:
library(shiny)
shinyUI(fluidPage(
headerPanel(title = "Volatility Slider"),
sidebarLayout(
sidebarPanel(
sliderInput("Risk","Volatility", 0, 0.24, 0.12)
),
mainPanel(
textOutput("Output")
)
)
))
server <- function(input, output) {
sliderValues <- reactive({
#This part finds the optimal portfolio using CAPM(which is found in a different script).
custom <- three_assets %>%
filter(sd_p > input$Risk,
sd_p < input$Risk+0.0001)
max_er_custom <- custom[custom$er_p == max(custom$er_p)]
toString(max_er_custom)
})
output$Output <- renderText({
sliderValues()
})
}
Here is a screenshot of the dashboard. The first three values are the weights of the three assets, the forth value is the expected return of that portfolio and the last value is the volatility of that portfolio all using historical data.

Answer 1

Not sure how to replicate your logic without your files, but here's an example where the input slider determines the values in the sliderValues data frame, which are in turn used to create a bar chart.
library(shiny); library(ggplot2)
ui <- fluidPage(
headerPanel(title = "Volatility Slider"),
sidebarLayout(
sidebarPanel(
sliderInput("Risk","Volatility", 0, 0.24, 0.12)
),
mainPanel(
plotOutput("Output")
)
)
)
server <- function(input, output) {
sliderValues <- reactive({
data.frame(values = c(input$Risk, 0.7 * (1 - input$Risk), 0.3 * (1-input$Risk)),
categories = c("A", "B", "C"))
})
output$Output <- renderPlot(
ggplot(sliderValues(), aes(1, values, fill = categories)) +
geom_col() +
coord_polar(theta = "y")
)}
shinyApp(ui = ui, server = server)