app.R

if(!require(pacman)){
    install.packages("pacman")
}
p_load(ggplot2, dplyr, janitor)
district <-c("A","B","C","A","B", "C")
money <-c(500,324,245,654,234, 232)
year <- c("2001", "2001", "2001", "2002", "2002", "2002")
df <- data.frame(district, money, year, stringsAsFactors = FALSE)
total_by_year <- df %>%
    group_by(year) %>%
    summarize(
        money = sum(money)
    ) %>%
    mutate(
        district = "All"
    ) %>%
    ungroup()
df_with_total <- bind_rows(df, total_by_year)
districts <- c("All", sort(unique(district)))

# Define UI for application that draws a bar chart
ui <- fluidPage(

    # Application title
    titlePanel("School Expenditure by Year"),

    # Dropdown
    sidebarLayout(
        sidebarPanel(
        selectInput("mydistrict", "Select District", choices = districts, selected = "All", )
        ),
        # Set a place to show a bar chart of spending
        mainPanel(
           
           plotOutput("distSpending")
        )
    )
)

# Define server logic required to draw the barchart
server <- function(input, output) {
    
    # filter data based on user input 
    my_graph_data <- reactive({
        dplyr::filter(df_with_total, district == input$mydistrict)
    })
    
    # draw the bar chart
    output$distSpending <- renderPlot({
        ggplot(my_graph_data(), aes(x=year, y=money)) + 
          geom_bar(stat="identity", color = "black", fill="#0072B2") +
            ggtitle(paste("District:", input$mydistrict)) +
            theme_minimal() +
            theme(panel.border = element_blank(), panel.grid.major = element_blank(),
                  plot.title = element_text(size = 18, face = "bold"),
            panel.grid.minor = element_blank(), axis.line = element_line(colour = "gray")) +
            scale_y_continuous(expand = c(0, 0)) 
        
    })
}

# Run the application 
shinyApp(ui = ui, server = server)