我的问题如下:
我有一个闪亮的应用程序,它根据用户输入显示可变数量的输出元素(例如,详细信息如下:使用闪亮动态添加绘图到网页).
但是,我还想向每个输出元素添加一个输入元素,允许用户为输出指定一些修饰符(例如,让用户选择将每个元素视为绘图还是表格,但可以概括为对可变数量的输出进行任何类型的修改)。
我认为最简单的方法是向每个元素添加一个 selectInput 元素,其中包含我希望用户拥有的选择。
我的问题是,每次渲染页面时, selectInput 元素似乎都会恢复到其初始值,因此更改它们没有效果(实际上,它们确实有一个效果,但随后它们被重置,效果是恢复)。
以下代码重现了该问题(根据@skasch对上述问题的回答进行修改):
server.R
library(shiny)
max_plots <- 5
shinyServer(function(input, output) {
# Insert the right number of plot output objects into the web page
output$plots <- renderUI({
plot_output_list <- lapply(1:input$n, function(i) {
modifier <- paste("select",i,sep="")
plotname <- paste("plot", i, sep="")
plottitle <- paste("plottitle", i, sep="")
tablename <- paste("tablename", i, sep="")
# By default I display a plot
disp <- plotOutput(plotname, height = 280, width = 250)
# modifier may not be in the input if this is the first time the element is displayed
if(modifier %in% names(input) && input[[modifier]] == "table") {
disp = tableOutput(tablename)
}
# Make the output element display properly:
tagList(
textOutput(plottitle, container = h3),
uiOutput(modifier),
disp)
})
# Convert the list to a tagList - this is necessary for the list of items
# to display properly.
do.call(tagList, plot_output_list)
})
# Call renderPlot for each one. Plots are only actually generated when they
# are visible on the web page.
for (i in 1:max_plots) {
# Need local so that each item gets its own number. Without it, the value
# of i in the renderPlot() will be the same across all instances, because
# of when the expression is evaluated.
local({
my_i <- i
modifier <- paste("select",i,sep="")
plotname <- paste("plot", my_i, sep="")
plottitle <- paste("plottitle", my_i, sep="")
tablename <- paste("tablename", my_i, sep="")
output[[plotname]] <- renderPlot({
plot(1:my_i, 1:my_i, xlim = c(1, max_plots), ylim = c(1, max_plots), main = paste("1:", my_i, ". n is ", input$n, sep = ""))
})
output[[plottitle]] <- renderText({paste("1:", my_i, ". n is ", input$n, sep = "")
})
output[[tablename]] <- renderTable({table(x = 1:my_i, y = 1:my_i)
})
# I suspect the problem is the re-evaluation of this part that resets the "selected" field
output[[modifier]] <- renderUI({selectInput(
inputId = modifier,
label="select how to display",
choices = c("plot","table"),
selected = 1)})
})
}
})
ui.r
library(shiny)
shinyUI(pageWithSidebar(
headerPanel("Dynamic number of plots"),
sidebarPanel(
sliderInput("n", "Number of plots", value=1, min=1, max=5)
),
mainPanel(
uiOutput("plots") # This is the dynamic UI for the plots
)
))