How can I use a slider in R Shiny to control the frequency by which a category is sampled? - shiny

Question

I want to use a slider in R Shiny to give the user control over the frequency a category is sampled from a data frame. The slider should have a default value of 0.5 (and range from 0 to 1), and at the default value (0.5), I have defined the frequency by which each category should be sampled. When the user adjusts the slider towards 1 (the maximum), I would like the frequencies of the highest categories to become even higher at the expense of the lowest frequency categories and vice-versa when the slider is adjusted towards 0 (the lowest frequency categories should increase, while the highest decrease). The frequencies should always sum to 1.
For example, I have a data frame that contains six categories and the frequencies by which each category is initially sampled. For instance:
df <- data.frame(food = c("fish", "shrimp", "chicken", "lamb", "beef", "tofu"), frequency = c(0.20, 0.06, 0.30, 0.10, 0.23, 0.11))
When the R Shiny slider is set to 1, I want the frequency of the initial highest category (chicken) to be 1.0, with the other categories being 0. As the slider goes to 1, I also want the next highest categories (beef and fish) to increase, but they should maintain the initial frequency order (with chicken remaining highest) until (as the slider gets closer to 1) they also go to 0 and chicken goes to 1.0. The highest categories (chicken, beef, and fish) should grow at the expense of the lowest categories (tofu, lamb, and shrimp), with shrimp (the lowest frequency) being the first to go to 0, followed by lamb and tofu.
I would like a similar (but opposite) process to occur as the slider goes to 0, with shrimp eventually being at a frequency of 1 (and lamb and tofu initially increasing at the expense of the higher frequency categories) and chicken being the first to go to 0 (followed by beef, fish, tofu, and lamb).
Essentially I need to rework the sample_data function in the example below:
library(shiny)
sample_data <- function(slider_value, data) {
adjusted_frequency <- data$frequency + (slider_value) * (max(data$frequency) - data$frequency)
data$sampled_frequency <- adjusted_frequency / sum(adjusted_frequency)
return(data)
}
ui <- fluidPage(
titlePanel("Input Data Using a Slider"),
sidebarLayout(
sidebarPanel(
sliderInput("value", "Enter a value:",
min = 0, max = 1, value = 0.5)
),
mainPanel(
tableOutput("data")
)
)
)
server <- function(input, output) {
df <- data.frame(food = c("fish", "shrimp", "chicken", "lamb", "beef", "tofu"), frequency = c(0.20, 0.06, 0.30, 0.10, 0.23, 0.11))
data <- reactive({
sample_data(input$value, df)
})
output$data <- renderTable({
data()
})
}
shinyApp(ui, server)
Right now, the slider I have gives the results as depicted in the image below:
When set to 0, it displays the default frequencies, and when set to 1 it has all categories at equal frequencies. How can I improve the sample_data function to accomplish the more complicated procedure I have described?
Thank you very much for your help!