Calculate in Shinyapps - r

Question

I want to calculate some values and return the values to my shiny app:
ui <- fluidPage(
sidebarLayout(
sidebarPanel(numericInput(inputId = "ME",
label = "Maternal effect:",
min = -1,
max = 1,
value = 0.5),
numericInput(inputId = "CE",
label = "Child effect:",
min = -1,
max = 1,
value = 0.5)
),
mainPanel(h3(textOutput("Power"))
)
)
)
server <- function(input, output) {
bzc <- sqrt(abs(input$CE)) * sign(input$CE)
bzm <- sqrt(abs(input$ME)) * sign(input$ME)
results <- bzc * bzm
output$Power <- renderPrint({results
})
}
shinyApp(ui = ui, server = server)
This doesnt apprear to work. Any tips on how to calculate in the shiny app?

Answer 1

The error-messages arise, because you have input-objects outside of the render-functions. If you want to calculate something, which you want to reuse in multiple plots, then use a reactive or observe-function.
For all other cases it is enough add the code for bzc, bzm and result inside the render-functions:
ui <- fluidPage(
sidebarLayout(
sidebarPanel(numericInput(inputId = "ME",
label = "Maternal effect:",
min = -1,
max = 1,
value = 0.5),
numericInput(inputId = "CE",
label = "Child effect:",
min = -1,
max = 1,
value = 0.5)
),
mainPanel(h3(textOutput("Power"))
)
)
)
server <- function(input, output) {
output$Power <- renderPrint({
bzc <- sqrt(abs(input$CE)) * sign(input$CE)
bzm <- sqrt(abs(input$ME)) * sign(input$ME)
results <- bzc * bzm
results
})
}
shinyApp(ui = ui, server = server)