我想将变量 input $ var 中的变量存储到一个对象,该对象可以与后者的字符串进行比较。现在,我只是试图通过将其存储到对象 value_stored 在屏幕上打印。但是它不打印任何内容*(错误:无法将类型'closure'强制转换为类型'character'*的向量)。这意味着它没有存储值。
library(shiny)
ui <- fluidPage(
titlePanel("censusVis"),
sidebarLayout(
sidebarPanel(
helpText("Create demographic maps with
information from the 2010 US Census."),
selectInput("var",
label = "Choose a variable to display",
choices = c("Percent White",
"Percent Black",
"Percent Hispanic",
"Percent Asian"),
selected = "Percent White")
),
mainPanel(
textOutput("selected_var")
textOutput("test")
)
)
)
server <- function(input, output) {
output$selected_var <- renderText({
paste(input$var)
})
value_store <- reactive(input$var)
output$test <- renderText({
paste(value_store)
})
# I want to use the value in input$var for some comparision.
# but value_store unable to store. Help.
}
shinyApp(ui = ui, server = server)
答案 0 :(得分:1)
我强烈建议使用reactiveValues
(用于存储您的无功值的对象)和observeEvent
。
使用服务器代码:
server <- function(input, output) {
# Create object for reactive values
rv <- reactiveValues(
value_store = character()
)
# When input changes -> update
observeEvent(input$var, {
output$selected_var <- renderText({
paste(input$var)
})
rv$value_store <- input$var
output$test <- renderText({
paste(rv$value_store)
})
})
}
PS:您可以删除paste
,因为那里没有任何作用。
答案 1 :(得分:0)
您快要准备好了,您只需要先定义反应性元素,然后在watchEvent()函数中监视输入即可。然后,在观察值内部,您可以使用isolate()更新值。
ui <- fluidPage(
titlePanel("censusVis"),
sidebarLayout(
sidebarPanel(
helpText("Create demographic maps with
information from the 2010 US Census."),
selectInput("var",
label = "Choose a variable to display",
choices = c("Percent White",
"Percent Black",
"Percent Hispanic",
"Percent Asian"),
selected = "Percent White")
),
mainPanel(
textOutput("selected_var")
textOutput("test")
)
)
)
server <- function(input, output) {
value_store <- reactive(val = '')
observeEvent(input$var, {
# add to reactive
isolate(value_store$val = input$var)
# or render update
output$selected_var <- renderText({
paste(value_store$val)
})
})
output$test <- renderText({
paste(value_store$val)
})
# I want to use the value in input$var for some comparision.
# but value_store unable to store. Help.
}
shinyApp(ui = ui, server = server)