Why am I getting 'server not found' error in my shiny app? - r

Question

I'm trying to learn shiny on my own and it's been very fun so far. I'm trying to plot a singular point on a graph with both inputs coming from the user. I am getting a "Error in shinyApp(ui = ui, server = server) : object 'server' not found". Here's my code:
ui <- fluidPage(
titlePanel("Title"),
sidebarPanel(
sliderInput(inputId ="x1", 'I', min = 4, max = 12, value = 4),
sliderInput(inputId = "y1", 'Y', min = 0, max = 10, value = 1)),
plotOutput("Scale")
)
server() <- function(input, output){
output$Scale <- renderPlot({
ggplot(aes_string(x = input$x1, y = input$y1))+
geom_point() })
}
shinyApp(ui = ui, server = server)

Answer 1

Here is a complete working example, I hope this will help.
The slider inputs will provide numerical information for your plot. This might be easier to conceptualize if placed in a data frame (see below).
The aes aesthetic mapping provides information on x and y axis for your plot, and uses data to indicate dataset to use for plot.
Finally, added limits to appreciate the point moving around the graph with slider changes (otherwise, the axis will automatically rescale).
Lots more you can learn on ggplot2 here:
https://ggplot2.tidyverse.org/
library(ggplot2)
library(shiny)
ui <- fluidPage(
titlePanel("Title"),
sidebarPanel(
sliderInput(inputId ="x1", 'I', min = 4, max = 12, value = 4),
sliderInput(inputId = "y1", 'Y', min = 0, max = 10, value = 1)),
plotOutput("Scale")
)
server <- function(input, output){
output$Scale <- renderPlot({
my_data <- data.frame(x = input$x1, y = input$y1)
ggplot(aes(x = x, y = y), data = my_data)+
geom_point() +
xlim(4, 12) +
ylim(0, 10)
})
}
shinyApp(ui = ui, server = server)