Shiny App in R: How to connect input and output - r

Question

I do not know how to connect input (n) in the slider and output (plot). When I move the bottom on the slider in the shinny app, the plot did not change. I am wondering if the output and input did not link together approporatedly.
library(ggplot2)
library(shiny)
plot<-function(x,y,xlim=c(-3,3)){
x <- seq(-4, 4, by=0.01)
norm_dens <- dnorm(x)
t_dens <- dt(x, df = n-1)
df = data.frame(x = x, z = norm_dens, t = t_dens)
ggplot(data = df, aes(x)) +
geom_line(aes(y = z, colour = "z"))+
geom_line(aes(y = t,color = "t"))+
labs(x="x", y = "")+
scale_color_manual(name = "l", values = c("z" = "blue", "t" = "red"))+
coord_cartesian(xlim = xlim)
}
plot(x,y)
## UI function
ui <- fluidPage(
mainPanel(
plotOutput(outputId="plot")),
fluidRow(
column(2,
"Sample Size",
sliderInput("n", label = "n", value = 5, min = 2, max = 100),step=1)
)
)
# Server logic
server <- function(input, output) {
reactive({
df %>%
filter(n %in% input$n)
})
output$plot<-renderPlot({
plot(x,y)
})
}
## Run shiny app
shinyApp(ui, server)

Answer 1

You don't need the reactive here. Try this:
library(ggplot2)
library(shiny)
plot<-function(x,y,xlim=c(-3,3),n){
x <- seq(-4, 4, by=0.01)
norm_dens <- dnorm(x)
t_dens <- dt(x, df = n-1)
df = data.frame(x = x, z = norm_dens, t = t_dens)
ggplot(data = df, aes(x)) +
geom_line(aes(y = z, colour = "z"))+
geom_line(aes(y = t,color = "t"))+
labs(x="x", y = "")+
scale_color_manual(name = "l", values = c("z" = "blue", "t" = "red"))+
coord_cartesian(xlim = xlim)
}
## UI function
ui <- fluidPage(
mainPanel(
plotOutput(outputId="plot")),
fluidRow(
column(2,
"Sample Size",
sliderInput("n", label = "n", value = 5, min = 2, max = 100),step=1)
)
)
# Server logic
server <- function(input, output) {
output$plot<-renderPlot({
req(input$n)
plot(x,y,n=input$n)
})
}
## Run shiny app
shinyApp(ui, server)`enter code here`