I'm trying publish a Shiny visual in an .rmd file. My code runs, but the output leaflet is compressed when I run the .rmd file. Any insights on how to make this "taller"?

ui1 <- fluidPage(
    titlePanel("Temperature per year by State"),
    sidebarLayout(
        sidebarPanel(
            inputPanel(
                selectInput(inputId = "input_year",
                            label = "Which Year do you want to display?",
                            choices = years,
                            selected = years))),
        
        mainPanel(
            plotOutput("plot1")
        )))
grouping <- 
    
    server1 <- function(input, output){
        output$plot1 <- renderPlot({
            ggplot(filter(dataset_new,
                          Year == input$input_year), 
                   mapping = aes(x = long, y = lat, group = group, fill = Average.temp))+
                geom_polygon(color = "black")+
                guides(fill = guide_legend(title = "Temperature\n(F)", 
                                           reverse = T))+
                labs(x = "Longitude",y = "Latitude", 
                     title = "Average temperature by U.S. State")+
                theme(panel.grid.major = element_blank(), 
                      panel.grid.minor = element_blank(),
                      panel.background = element_blank(), 
                      axis.line = element_line(colour = "black"))+
                annotate("text", x = -115, y = 27, label = "***Temperature information for\nNevada, New Mexico and\n Oklahoma was not available") +
                scale_fill_gradient(low = "yellow", high = "red")
        })}
shinyApp(ui = ui1, server = server1)
 
     
    