shin R中的被动数据帧和更新输入问题

我仍然是使用shiny的初学者（下面的代码将清楚地演示这一事实）。在我正在做的这个例子中，我必须生成两个条形图。这两个图都是从一组数据框中衍生出来的，每个数据框都与不同的年份相关。在每个数据帧中都有一些行（示例中为8行），每个行与一个值（例如，“值1”、“值2”等）关联。用户选择年份范围（

start\u year

和

end\u year

），服务器计算两年之间每个值的差值（例如，2018年的“值1”减去2015年的“值1”）。但是，在第一个条形图中仅显示有限数量的值，在本例中为4。到目前为止，我还没有遇到任何问题。但是，我必须显示另一个条形图，链接到示例中的输入

val\u select

。我必须为该输入添加第一个条形图中显示的前四个值作为选项。此外，用户可以从该短值列表中进行选择，并且在第二个条形图中，将显示所选年份期间内每年所选值的趋势。例如，如果在2005-2018年期间，显示的四个值是，例如，“值2”、“值4”、“值6”、“值7”，则可以在第三个输入中从这四个值中进行选择，所选值将显示在第二个条形图中，其值介于2005年和2018年之间。 我在脚本中有两个主要问题：

尝试用

updateSelectInput

更新第三个输入

val_select

中的选项列表会压碎应用程序

第二个条形图不会生成并返回以下错误：

下面是我在线程结束时编写的示例，试图获得所需的输出

library(shiny)
library(shinydashboard)
library(highcharter)
library(dplyr)

# Generate data
years = c(2009:2019)

list_db = vector("list")
var = c("Value 1", "Value 2", "Value 3", "Value 4", "Value 5", "Value 6", "Value 7", "Value 8")

for (i in 1:length(years)){
    x = runif(8, min = 0, max = 100)
    df = data.frame(var, x)
    list_db[[i]] = df
}
names(list_db) = years

# UI
ui <- dashboardPage(
    dashboardHeader(),
    dashboardSidebar(
        sidebarMenu(
            menuItem("Page 1", tabName = 'tab_page_1'),
            selectInput(inputId = "start_year",
                        label = "Select starting year:",
                        choices = min(years):max(years)),
            selectInput(inputId = "end_year",
                        label = "Select ending year:",
                        choices = min(years):max(years)),
            selectInput(inputId = "val_select",
                        label = "Select Value (within the selected range) to show:",
                        choices = var)
        )
    ),
    dashboardBody(
        tabItem(tabName = 'tab_page_1'),
        fluidPage(
            titlePanel("Example Page 1")
        ),
        fluidPage(
            fluidRow(
                box(title = "Barplot n.1",
                    solidHeader = TRUE, 
                    status = 'primary',
                    highchartOutput("tab_1", height = 500)
                ),
                box(title = "Barplot n.2 (Value focus)",
                    solidHeader = TRUE, 
                    status = 'primary',
                    highchartOutput("tab_2", height = 500)
                ),
                
            )
        )
    )
)

# Server
server <- function(input, output, session) {
    
    # Update 'end_year' based on 'start_year' input
    
    observeEvent(input$start_year, {
        updateSelectInput(session, 'end_year',
                          choices = (as.integer(input$start_year)+1):max(years)
        )
    })
    
    # Reactive data frame
    
    react_data = reactive({
        
        # Generate starting and ending data frame
        assign("data_start", list_db[[as.character(input$start_year)]])
        assign("data_end", list_db[[as.character(input$end_year)]])
        
        # Add the selected year to variables' names
        data_start = data_start %>% rename_at(vars(-var), ~ paste0(., "_", input$start_year))
        data_end = data_end %>% rename_at(vars(-var), ~ paste0(., "_", input$end_year))
        
        # Join starting and ending data frame
        dt = full_join(data_start, data_end, by = "var")
        
        # Calculate vars' differences between the selected years
        dt$x_diff = dt[,paste0("x_",input$end_year)] - dt[,paste0("x_",input$start_year)] 
        
        # Select only first 4 Values
        dt = head(dt[order(dt$x_diff),],4)
        
    })

    # Update 'val_select' b <--- Problematic
    
    observeEvent({
        val_select_data = react_data()
        mylist = val_select_data$var
        updateSelectInput(session, 'val_select',
                          choices = mylist
        )
    })
    
    # Output 'tab_1' <--- This works
    
    output$tab_1 = renderHighchart({ 
        
        # Select data frame
        mydata1 = react_data()
        
        # Plot
        highchart() %>% 
            hc_chart(type = "bar") %>%
            hc_xAxis(categories = mydata1$var)  %>%
            hc_series(list(name = "Variables", 
                           pointWidth = 50, 
                           data = mydata1$x_diff, 
                           color = "rgba(162, 52, 52, 0.5)")) %>%
            hc_xAxis(labels = list(style = list(fontSize = "12"))) %>%
            hc_chart(plotBackgroundColor = "#EEEEEE") %>%
            hc_legend(enabled = FALSE)
    })
    
    # Output 'tab_2' <--- Problematic
    
    output$tab_2 = renderHighchart({ 
        
        # Select data frame
        mydata2 = react_data()
        
        # List of first 4 Value in the selected year range
        first_values = mydata2$var
        
        # List of years in the selected year range
        years = sort(c(min(input$start_year):max(input$end_year)))
        
        # Create a list to contain data frame for each year (inside the selected range)
        data_year = vector("list", length(years))
        
        for (i in as.character(years)){
            
            assign("df", list_db[[i]])
            
            # Consider only Value in 'first_values'
            df = df[df$var %in% first_values,]
            
            # Insert into the list
            data_year[[i]] = df
            
        }
        # Remove empty elements from the list
        data_year = data_year[!sapply(data_year,is.null)]
        
        # Generate a yearly data frame for each Value
        data_values = vector("list", length(first_values))
        years_lead = years[-1]
        
        for (row in 1:length(data_values)){
            
            df = data_year[[as.character(years[1])]][row, c(1:length(data_year[[as.character(years[1])]]))]
            
            for (i in years_lead){
                df = rbind(df, data_year[[as.character(i)]][row, c(1:length(data_year[[as.character(i)]]))])
            }
            
            df = cbind(years, df)
            data_values[[row]] = df
            
        }
        
        # Assign names to the list
        names(data_values) = paste(first_values)
        
        # Select the dataframe based on the selected profession
        assign("plot_data", data_values[[as.character(input$val_select)]])
        
        # Plot
        highchart() %>% 
            hc_title(text = input$val_select) %>%
            hc_subtitle(text = "Trend in the considerd period") %>%
            hc_chart(type = "column") %>%
            hc_add_series(name = "Amount",
                          data = plot_data,
                          type = "column",
                          hcaes(x = plot_data$years, y =  plot_data$x),
                          color = "rgba(0, 102, 102, 0.6)",
                          yAxis = 0) %>%
            hc_xAxis(labels = list(style = list(fontSize = "12")),
                     opposite = FALSE) %>%
            hc_chart(plotBackgroundColor = "#EEEEEE") %>%
            hc_legend(enabled = FALSE)
    })
    
}

# UI
shinyApp(ui = ui, server = server)

库（闪亮）
图书馆（shinydashboard）
图书馆（高级特许）
图书馆（dplyr）
#生成数据
年份=c（2009:2019）
列表=向量（“列表”）
var=c（“价值1”、“价值2”、“价值3”、“价值4”、“价值5”、“价值6”、“价值7”、“价值8”）
（一分之一：长度（年））{
x=runif（8，最小值=0，最大值=100）
df=数据帧（变量，x）
列表_db[[i]]=df
}
姓名（名单）＝年
#用户界面
ui%
hc_系列（列表（name=“变量”，
点宽度=50，
数据=mydata1$x_差异，
color=“rgba（162,52,52,0.5）”）%>%
hc_xAxis（标签=列表（样式=列表（fontSize=“12”））%>%
hc#U图表（plotBackgroundColor=“#EEEEEE”）%>%
hc_图例（启用=错误）
})
#输出'tab_2'%
hc_标题（文本=输入$val_选择）%>%
hc_副标题（text=“考虑期内的趋势”）%>%
hc_图表（type=“column”）%>%
hc_添加_系列（name=“Amount”，
数据=绘图数据，
type=“column”，
hcaes（x=绘图数据$years，y=绘图数据$x），
color=“rgba（0,102,102,0.6）”，
yAxis=0）%>%
hc_xAxis（标签=列表（样式=列表（fontSize=“12”）），
相反=假）%>%
hc#U图表（plotBackgroundColor=“#EEEEEE”）%>%
hc_图例（启用=错误）
})
}
#用户界面
shinyApp（用户界面=用户界面，服务器=服务器）

---

提前感谢任何能给我一些建议的人，我为我可能的“笨拙”代码提前道歉。

第二个

观察事件

不起作用，因为您没有考虑空值。此外，最初的开始年和结束年是相同的，应该在反应性数据中加以说明。修复此部分后，左侧的图形很好，第二个图形的数据也很好。但是，我不确定这是否是您要在右侧绘制的数据。确定后，需要调整

输出$tab_2

中第二个highchart的语法。请尝试以下代码：

library(DT)

# Generate data
years = c(2009:2019)

list_db = vector("list")
var = c("Value 1", "Value 2", "Value 3", "Value 4", "Value 5", "Value 6", "Value 7", "Value 8")

for (i in 1:length(years)){
  x = runif(8, min = 0, max = 100)
  df = data.frame(var, x)
  list_db[[i]] = df
}
names(list_db) = years

# UI
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(
    sidebarMenu(
      menuItem("Page 1", tabName = 'tab_page_1'),
      selectInput(inputId = "start_year",
                  label = "Select starting year:",
                  choices = min(years):max(years)),
      selectInput(inputId = "end_year",
                  label = "Select ending year:",
                  choices = min(years):max(years)),
      selectInput(inputId = "val_select",
                  label = "Select Value (within the selected range) to show:",
                  choices = var)
    )
  ),
  dashboardBody(
    tabItem(tabName = 'tab_page_1'),
    fluidPage(
      titlePanel("Example Page 1")
    ),
    fluidPage(
      useShinyjs(),
      fluidRow(
        box(title = "Barplot n.1",
            solidHeader = TRUE, 
            status = 'primary', 
            highchartOutput("tab_1", height = 500)
        ),
        box(title = "Barplot n.2 (Value focus)",
            solidHeader = TRUE, 
            status = 'primary',  DTOutput("tb2")
            #highchartOutput("tab_2", height = 500)
        ),
        
      )
    )
  )
)

# Server
server <- function(input, output, session) {
  plotme <- reactiveValues(data=NULL)
  # Update 'end_year' based on 'start_year' input
  
  observeEvent(input$start_year, {
    updateSelectInput(session, 'end_year',
                      choices = (as.integer(input$start_year)+1):max(years)
    )
  })
  
  # Reactive data frame
  
  react_data <- reactive({
    req(input$start_year,input$end_year)
    
    if (input$start_year == input$end_year){
      dt <- NULL
    }else {
      # Generate starting and ending data frame
      assign("data_start", list_db[[as.character(input$start_year)]])
      assign("data_end", list_db[[as.character(input$end_year)]])
      
      # Add the selected year to variables' names
      data_start = data_start %>% rename_at(vars(-var), ~ paste0(., "_", input$start_year))
      data_end = data_end %>% rename_at(vars(-var), ~ paste0(., "_", input$end_year))
      
      # Join starting and ending data frame
      dt = full_join(data_start, data_end, by = "var")
      
      # Calculate vars' differences between the selected years
      dt$x_diff = dt[,paste0("x_",input$end_year)] - dt[,paste0("x_",input$start_year)] 
      
      # Select only first 4 Values
      dt = head(dt[order(dt$x_diff),],4)
    }
    dt
    
  })
  
  output$tb1 <- renderDT(react_data())
  
  # Update 'val_select' b <--- Problem fixed when you account for react_data() not being NULL
  
  observeEvent(list(input$start_year,input$end_year), {
    if (!is.null(react_data())) {
      mylist <- as.character(react_data()[,1])
      updateSelectInput(session, 'val_select', choices = mylist )
    }
  })
  
  # Output 'tab_1' <--- This works
  
  output$tab_1 = renderHighchart({ 
    if (is.null(react_data())) return(NULL)
    # Select data frame
    mydata1 = react_data()
    
    # Plot
    highchart() %>% 
      hc_chart(type = "bar") %>%
      hc_xAxis(categories = mydata1$var)  %>%
      hc_series(list(name = "Variables", 
                     pointWidth = 50, 
                     data = mydata1$x_diff, 
                     color = "rgba(162, 52, 52, 0.5)")) %>%
      hc_xAxis(labels = list(style = list(fontSize = "12"))) %>%
      hc_chart(plotBackgroundColor = "#EEEEEE") %>%
      hc_legend(enabled = FALSE)
  })
  
  observe({
    req(input$start_year,input$end_year,input$val_select)
    if (is.null(react_data())) return(NULL)
    # Select data frame
    mydata2 = react_data()
    
    # List of first 4 Value in the selected year range
    first_values = mydata2$var
    
    # List of years in the selected year range
    years = sort(c(min(as.numeric(input$start_year)):max(as.numeric(input$end_year))))
    
    # Create a list to contain data frame for each year (inside the selected range)
    data_year = vector("list", length(years))
    
    for (i in as.character(years)){
      
      assign("df", list_db[[i]])
      
      # Consider only Value in 'first_values'
      df = df[df$var %in% first_values,]
      
      # Insert into the list
      data_year[[i]] = df
      
    }
    # Remove empty elements from the list
    data_year = data_year[!sapply(data_year,is.null)]
    
    # Generate a yearly data frame for each Value
    data_values = vector("list", length(first_values))
    years_lead = years[-1]
    
    for (row in 1:length(data_values)){
      
      df = data_year[[as.character(years[1])]][row, c(1:length(data_year[[as.character(years[1])]]))]
      
      for (i in years_lead){
        df = rbind(df, data_year[[as.character(i)]][row, c(1:length(data_year[[as.character(i)]]))])
      }
      
      df = cbind(years, df)
      data_values[[row]] = df
      
    }
    
    # Assign names to the list
    names(data_values) = paste(first_values)
    
    # Select the dataframe based on the selected profession
    assign("plot_data", data_values[[as.character(input$val_select)]])
    plotme$data <- plot_data
    
    output$tb2 <- renderDT(plotme$data)
    
    # Output 'tab_2' <--- Problematic  - needs some work to fix the highchart
    
    output$tab_2 = renderHighchart({
      plot_data <- plotme$data
      if (is.null(plot_data)) return(NULL)
      # Plot
      plot_data %>% 
      highchart() %>% 
        hc_title(text = unique(plot_data$var)) %>%
        hc_subtitle(text = "Trend in the considerd period") %>%
        hc_chart(type = "column") %>%
        hc_add_series(name = "Amount",
                      #data = plot_data,
                      type = "column",
                      hcaes(x = plot_data$years, y =  plot_data$x),
                      color = "rgba(0, 102, 102, 0.6)",
                      yAxis = 0) %>%
        hc_xAxis(labels = list(style = list(fontSize = "12")),
                 opposite = FALSE) %>%
        hc_chart(plotBackgroundColor = "#EEEEEE") %>%
        hc_legend(enabled = FALSE)
    })
  })
  
}

# UI
shinyApp(ui = ui, server = server)

库（DT）
#生成数据
年份=c（2009:2019）
列表=向量（“列表”）
var=c（“价值1”、“价值2”、“价值3”、“价值4”、“价值5”、“价值6”、“价值7”、“价值8”）
（一分之一：长度（年））{
x=runif（8，最小值=0，最大值=100）
df=数据帧（变量，x）
列表_db[[i]]=df
}
姓名（名单）＝年
#用户界面
ui%
hc_添加_系列（name=“Amount”，
#数据=绘图数据，
type=“column”，
hcaes（x=绘图数据$years，y=绘图数据$x），
color=“rgba（0,102,102,0.6）”，
yAxis=0）%>%
hc_xAxis（标签=列表（样式=列表（fontSize=“12”）），
相反=假）%>%
hc#U图表（plotBackgroundColor=“#EEEEEE”）%>%
hc_图例（启用=错误）
})
})
}
#用户界面
shinyApp（用户界面=用户界面，服务器=服务器）

---

非常感谢@YBS的友好回答。经过一些调整，它成功了。 我必须对

mylist

和

first\u值进行排序，以便在输入“选择值（在所选范围内）显示”中的所选选项与显示的表格/条形图之间建立对应关系。此外，第二个条形图的问题与我给垂直轴的名称有关…'我为这样的选择感到羞耻。事实上，我已经厌倦了
ggplot2
，它成功了。然后，通过重命名变量，脚本工作正常。再次感谢你。下面是我根据你的建议修改的编辑脚本

library(shiny)
library(shinydashboard)
library(highcharter)
library(dplyr)
library(DT)

# Generate data
years = c(2009:2019)

list_db = vector("list")
var = c("Value 1", "Value 2", "Value 3", "Value 4", "Value 5", "Value 6", "Value 7", "Value 8")

for (i in 1:length(years)){
    x = runif(8, min = 0, max = 100)
    df = data.frame(var, x)
    list_db[[i]] = df
}
names(list_db) = years

# UI
ui <- dashboardPage(
    dashboardHeader(),
    dashboardSidebar(
        sidebarMenu(
            menuItem("Page 1", tabName = 'tab_page_1'),
            selectInput(inputId = "start_year",
                        label = "Select starting year:",
                        choices = min(years):max(years)),
            selectInput(inputId = "end_year",
                        label = "Select ending year:",
                        choices = min(years):max(years)),
            selectInput(inputId = "val_select",
                        label = "Select Value (within the selected range) to show:",
                        choices = var)
        )
    ),
    dashboardBody(
        tabItem(tabName = 'tab_page_1'),
        fluidPage(
            titlePanel("Example Page 1")
        ),
        fluidPage(
            fluidRow(
                box(title = "Barplot n.1",
                    solidHeader = TRUE, 
                    status = 'primary',
                    highchartOutput("tab_1", height = 500)
                ),
                box(title = "Table n.1 (Value focus)",
                    solidHeader = TRUE, 
                    status = 'primary',
                    DTOutput("tab_2")
                ),
                box(title = "Barplot n.2 (Value focus)",
                    solidHeader = TRUE, 
                    status = 'primary',
                    highchartOutput("tab_3", height = 500)
                )
            )
        )
    )
)

# Server
server <- function(input, output, session) {
    
    plotme = reactiveValues(data = NULL)
    
    # Update 'end_year' based on 'start_year' input
    
    observeEvent(input$start_year, {
        updateSelectInput(session, 'end_year',
                          choices = (as.integer(input$start_year)+1):max(years)
        )
    })
    
    # Reactive data frame
    
    react_data = reactive({
        
        req(input$start_year, input$end_year)
        
        if (input$start_year == input$end_year){
            dt = NULL
        } else {
        
        # Generate starting and ending data frame
        assign("data_start", list_db[[as.character(input$start_year)]])
        assign("data_end", list_db[[as.character(input$end_year)]])
        
        # Add the selected year to variables' names
        data_start = data_start %>% rename_at(vars(-var), ~ paste0(., "_", input$start_year))
        data_end = data_end %>% rename_at(vars(-var), ~ paste0(., "_", input$end_year))
        
        # Join starting and ending data frame
        dt = full_join(data_start, data_end, by = "var")
        
        # Calculate vars' differences between the selected years
        dt$x_diff = dt[,paste0("x_",input$end_year)] - dt[,paste0("x_",input$start_year)] 
        
        # Select only first 4 Values
        dt = head(dt[order(dt$x_diff),],4)
        
        }
        
        dt
        
    })

    # Update 'val_select' 
    
    observeEvent(list(input$start_year,input$end_year), {
        if (!is.null(react_data())) {
            mylist = as.character(react_data()[,1])
            updateSelectInput(session, 'val_select', choices = sort(mylist))
        }
    })
    
    # Output 'tab_1' 
    
    output$tab_1 = renderHighchart({ 
        
        # Select data frame
        mydata1 = react_data()
        
        # Plot
        highchart() %>% 
            hc_chart(type = "bar") %>%
            hc_xAxis(categories = mydata1$var)  %>%
            hc_series(list(name = "Variables", 
                           pointWidth = 50, 
                           data = mydata1$x_diff, 
                           color = "rgba(162, 52, 52, 0.5)")) %>%
            hc_xAxis(labels = list(style = list(fontSize = "12"))) %>%
            hc_chart(plotBackgroundColor = "#EEEEEE") %>%
            hc_legend(enabled = FALSE)
    })
    
    # Output 'tab_2' and 'tab_3'
    
    observe({
        req(input$start_year,input$end_year,input$val_select)
        if (is.null(react_data())) return(NULL)
        
        # Select data frame
        mydata2 = react_data()
        
        # List of first 4 Value in the selected year range
        first_values = mydata2$var
        first_values = sort(first_values)
        
        # List of years in the selected year range
        years = sort(c(min(as.numeric(input$start_year)):max(as.numeric(input$end_year))))
        
        # Create a list to contain data frame for each year (inside the selected range)
        data_year = vector("list", length(years))
        
        for (i in as.character(years)){
            
            assign("df", list_db[[i]])
            
            # Consider only Value in 'first_values'
            df = df[df$var %in% first_values,]
            
            # Insert into the list
            data_year[[i]] = df
            
        }
        # Remove empty elements from the list
        data_year = data_year[!sapply(data_year,is.null)]
        
        # Generate a yearly data frame for each Value
        data_values = vector("list", length(first_values))
        years_lead = years[-1]
        
        for (row in 1:length(data_values)){
            
            df = data_year[[as.character(years[1])]][row, c(1:length(data_year[[as.character(years[1])]]))]
            
            for (i in years_lead){
                df = rbind(df, data_year[[as.character(i)]][row, c(1:length(data_year[[as.character(i)]]))])
            }
            
            df = cbind(years, df)
            data_values[[row]] = df
            
        }
        
        # Assign names to the list
        names(data_values) = paste(first_values)
        
        # Select the dataframe based on the selected value
        assign("plot_data", data_values[[as.character(input$val_select)]])
        
        plotme$data = plot_data
        
        # Plot table 'tab_2'
        
        output$tab_2 = renderDT(plotme$data)
        
        # Plot table 'tab_3'
        
        output$tab_3 = renderHighchart({
            
            #plot_data = plotme$data
            if (is.null(plot_data)) return(NULL)
            
            names(plot_data)[names(plot_data) == 'x'] = 'variable'

            highchart() %>% 
                hc_title(text = unique(plot_data$var)) %>%
                hc_subtitle(text = "Trend in the considerd period") %>%
                hc_chart(type = "column") %>%
                hc_add_series(name = "Amount",
                              data = plot_data,
                              type = "column",
                              hcaes(x = years, y = variable),
                              color = "rgba(0, 102, 102, 0.6)",
                              yAxis = 0) %>%
                hc_xAxis(labels = list(style = list(fontSize = "12")),
                         opposite = FALSE) %>%
                hc_chart(plotBackgroundColor = "#EEEEEE") %>%
                hc_legend(enabled = FALSE)
            
            })
        
    })
    
}

# UI
shinyApp(ui = ui, server = server)

库（闪亮）
图书馆（shinydashboard）
图书馆（高级特许）
图书馆（dplyr）
图书馆（DT）
#生成数据
年份=c（2009:2019）
列表=向量（“列表”）
var=c（“价值1”、“价值2”、“价值3”、“价值4”、“价值5”、“价值6”、“价值7”、“价值8”）
（一分之一：长度（年））{
x=runif（8，最小值=0，最大值=100）
df=数据帧（变量，x）
列表_db[[i]]=df
}
姓名（名单）＝年
#用户界面
ui%
hc_图表（type=“bar”）%>%
library(shiny)
library(shinydashboard)
library(highcharter)
library(dplyr)
library(DT)

# Generate data
years = c(2009:2019)

list_db = vector("list")
var = c("Value 1", "Value 2", "Value 3", "Value 4", "Value 5", "Value 6", "Value 7", "Value 8")

for (i in 1:length(years)){
    x = runif(8, min = 0, max = 100)
    df = data.frame(var, x)
    list_db[[i]] = df
}
names(list_db) = years

# UI
ui <- dashboardPage(
    dashboardHeader(),
    dashboardSidebar(
        sidebarMenu(
            menuItem("Page 1", tabName = 'tab_page_1'),
            selectInput(inputId = "start_year",
                        label = "Select starting year:",
                        choices = min(years):max(years)),
            selectInput(inputId = "end_year",
                        label = "Select ending year:",
                        choices = min(years):max(years)),
            selectInput(inputId = "val_select",
                        label = "Select Value (within the selected range) to show:",
                        choices = var)
        )
    ),
    dashboardBody(
        tabItem(tabName = 'tab_page_1'),
        fluidPage(
            titlePanel("Example Page 1")
        ),
        fluidPage(
            fluidRow(
                box(title = "Barplot n.1",
                    solidHeader = TRUE, 
                    status = 'primary',
                    highchartOutput("tab_1", height = 500)
                ),
                box(title = "Table n.1 (Value focus)",
                    solidHeader = TRUE, 
                    status = 'primary',
                    DTOutput("tab_2")
                ),
                box(title = "Barplot n.2 (Value focus)",
                    solidHeader = TRUE, 
                    status = 'primary',
                    highchartOutput("tab_3", height = 500)
                )
            )
        )
    )
)

# Server
server <- function(input, output, session) {
    
    plotme = reactiveValues(data = NULL)
    
    # Update 'end_year' based on 'start_year' input
    
    observeEvent(input$start_year, {
        updateSelectInput(session, 'end_year',
                          choices = (as.integer(input$start_year)+1):max(years)
        )
    })
    
    # Reactive data frame
    
    react_data = reactive({
        
        req(input$start_year, input$end_year)
        
        if (input$start_year == input$end_year){
            dt = NULL
        } else {
        
        # Generate starting and ending data frame
        assign("data_start", list_db[[as.character(input$start_year)]])
        assign("data_end", list_db[[as.character(input$end_year)]])
        
        # Add the selected year to variables' names
        data_start = data_start %>% rename_at(vars(-var), ~ paste0(., "_", input$start_year))
        data_end = data_end %>% rename_at(vars(-var), ~ paste0(., "_", input$end_year))
        
        # Join starting and ending data frame
        dt = full_join(data_start, data_end, by = "var")
        
        # Calculate vars' differences between the selected years
        dt$x_diff = dt[,paste0("x_",input$end_year)] - dt[,paste0("x_",input$start_year)] 
        
        # Select only first 4 Values
        dt = head(dt[order(dt$x_diff),],4)
        
        }
        
        dt
        
    })

    # Update 'val_select' 
    
    observeEvent(list(input$start_year,input$end_year), {
        if (!is.null(react_data())) {
            mylist = as.character(react_data()[,1])
            updateSelectInput(session, 'val_select', choices = sort(mylist))
        }
    })
    
    # Output 'tab_1' 
    
    output$tab_1 = renderHighchart({ 
        
        # Select data frame
        mydata1 = react_data()
        
        # Plot
        highchart() %>% 
            hc_chart(type = "bar") %>%
            hc_xAxis(categories = mydata1$var)  %>%
            hc_series(list(name = "Variables", 
                           pointWidth = 50, 
                           data = mydata1$x_diff, 
                           color = "rgba(162, 52, 52, 0.5)")) %>%
            hc_xAxis(labels = list(style = list(fontSize = "12"))) %>%
            hc_chart(plotBackgroundColor = "#EEEEEE") %>%
            hc_legend(enabled = FALSE)
    })
    
    # Output 'tab_2' and 'tab_3'
    
    observe({
        req(input$start_year,input$end_year,input$val_select)
        if (is.null(react_data())) return(NULL)
        
        # Select data frame
        mydata2 = react_data()
        
        # List of first 4 Value in the selected year range
        first_values = mydata2$var
        first_values = sort(first_values)
        
        # List of years in the selected year range
        years = sort(c(min(as.numeric(input$start_year)):max(as.numeric(input$end_year))))
        
        # Create a list to contain data frame for each year (inside the selected range)
        data_year = vector("list", length(years))
        
        for (i in as.character(years)){
            
            assign("df", list_db[[i]])
            
            # Consider only Value in 'first_values'
            df = df[df$var %in% first_values,]
            
            # Insert into the list
            data_year[[i]] = df
            
        }
        # Remove empty elements from the list
        data_year = data_year[!sapply(data_year,is.null)]
        
        # Generate a yearly data frame for each Value
        data_values = vector("list", length(first_values))
        years_lead = years[-1]
        
        for (row in 1:length(data_values)){
            
            df = data_year[[as.character(years[1])]][row, c(1:length(data_year[[as.character(years[1])]]))]
            
            for (i in years_lead){
                df = rbind(df, data_year[[as.character(i)]][row, c(1:length(data_year[[as.character(i)]]))])
            }
            
            df = cbind(years, df)
            data_values[[row]] = df
            
        }
        
        # Assign names to the list
        names(data_values) = paste(first_values)
        
        # Select the dataframe based on the selected value
        assign("plot_data", data_values[[as.character(input$val_select)]])
        
        plotme$data = plot_data
        
        # Plot table 'tab_2'
        
        output$tab_2 = renderDT(plotme$data)
        
        # Plot table 'tab_3'
        
        output$tab_3 = renderHighchart({
            
            #plot_data = plotme$data
            if (is.null(plot_data)) return(NULL)
            
            names(plot_data)[names(plot_data) == 'x'] = 'variable'

            highchart() %>% 
                hc_title(text = unique(plot_data$var)) %>%
                hc_subtitle(text = "Trend in the considerd period") %>%
                hc_chart(type = "column") %>%
                hc_add_series(name = "Amount",
                              data = plot_data,
                              type = "column",
                              hcaes(x = years, y = variable),
                              color = "rgba(0, 102, 102, 0.6)",
                              yAxis = 0) %>%
                hc_xAxis(labels = list(style = list(fontSize = "12")),
                         opposite = FALSE) %>%
                hc_chart(plotBackgroundColor = "#EEEEEE") %>%
                hc_legend(enabled = FALSE)
            
            })
        
    })
    
}

# UI
shinyApp(ui = ui, server = server)