User defined function output in Shiny not in scope - shiny

Question

I would like to use a user defined function in Shiny to perform a simple calculation with output two variables. The function I wrote works when it is not part of a shiny app. However when part of a Shiny, the returned object (dfr) is ‘not in scope’. What am I missing?
library(shiny)
# Function ----------------------------------------------------------------
convert <- function(coef_1, coef_2, vec) {
part_1 <- coef_1/(2*sin((vec/2)*pi/180))
part_2 <- 2*(180/pi)*(asin(coef_2/(2*part_1)))
dfr <- data.frame(part_1, part_2)
return(dfr)
}
# End Function ------------------------------------------------------------
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
textInput("num", h3("Enter number to convert:"), value = NULL)
),
mainPanel(
verbatimTextOutput("text1", placeholder = TRUE),
verbatimTextOutput("text2", placeholder = TRUE)
)
)
)
server <- function(input, output) {
nums_str <- as.character(input$num)
nums_vector <- as.numeric(unlist(strsplit(nums_str, split = ",")))
convert(1.5, 1.1, nums_vector)
output$text1 <- renderText({
req(input$num)
dfr$part_1
})
output$text2 <- renderText({
req(input$num)
dfr$part_2
})
}
shinyApp(ui = ui, server = server)

Answer 1

When you use inputs, you need to do it in reactive environment, such as reactive(), renderDataTable(), etc.
Here, you need to run your function in a reactive() and then call it with dfr() in the outputs.
server <- function(input, output) {
dfr <- reactive({
convert(1.5, 1.1, as.numeric(input$num))
})
output$text1 <- renderText({
req(input$num)
dfr()$part_1
})
output$text2 <- renderText({
req(input$num)
dfr()$part_2
})
}
Since this is quite basic stuff with R Shiny, checking some tutorials might be very useful.