[英]Storing a reactive output in a vector - Shiny R
我正在构建一个 shiny 应用程序。 我使用了一些过滤器并渲染了一个数据框,并且数据框根据用户输入动态变化。 但是我无法将数据框中的特定列值存储到向量中。 我需要将每次反应的 output 存储到一个向量中,以便以后可以再次使用这些值。 这里的值存储在 text_vec 中,我需要将其传递到 API 但我无法从 text_vec 访问值,我必须每次将更新后的值传递到 API
library(dplyr)
library(shiny)
shinyApp(ui = fluidPage(
sidebarLayout(
sidebarPanel(
selectInput(inputId = "cyl",
label = "Number cylinders:",
choices = c("all",sort(unique(mtcars$cyl))),
selected = "all"),
actionButton("capture",
"capture value")
), # closes sidebarPanel
mainPanel(
tableOutput("text"),
tableOutput("text2"),
tableOutput("text3"),
tableOutput("table")
) # closes mainPanel
) # closes sidebarLayout
), # closes fluidPage
server = function(input, output) {
# some example reactive data
cars_react <- reactive({
mtcars %>%
filter(cyl == input$cyl | input$cyl == "all")
})
# simply global assignment of a reactive vector
observeEvent(cars_react(), {
# here is a globally assigned vector taken from the reactive data
# reused in a render statement it will not react to change, since it is not reactive
test_vec3 <<- unique(cars_react()$hp)
})
# here a file is written to the working directory of your shiny app
# everytime cars_react() changes write (and overwrite) vector to a file
observeEvent(cars_react(), {
test_vec = unique(cars_react()$hp)
saveRDS(test_vec, file = "test_vec.Rdata")
})
# same as above but the file is gradually growing and not overwritten
# everytime cars_react() changes add vector to a (over several sessions growing) list
observeEvent(cars_react(), {
test_vec2 = unique(cars_react()$hp)
if (file.exists("test_list.Rdata")) {
temp = readRDS("test_list.Rdata")
test_list = c(temp, list(test_vec2))
} else {
test_list = list(test_vec2)
}
saveRDS(test_list, file = "test_list.Rdata")
})
# here we access the reactive data with isolate and make it non-reactive, but can update the values through a button click
text_vec <<- eventReactive(input$capture, {
isolate(unique(cars_react()$hp))
})
# output of our reactive data as table
output$table <- renderTable({
cars_react()
})
# text output of globally assigned non-reactive vector test_vec3 (not changing!)
output$text <- renderText({
test_vec3
})
# you can capture values of reactives with isolate, but then, they don't change anymore
# text output of isolated formely reactive vector unique(cars_react()$hp (not changing!)
output$text2 <- renderText({
isolate(unique(cars_react()$hp))
})
# text output of new reactive vector (changes when input$capture button is clicked)
output$text3 <- renderText({
text_vec()
})
for (i in text_vec)
{
url = "https://oscar.com/prweb/PRRestService/"
parameters<-'{
{
"Reference":"Account"
,"ReferenceValue":""
}'
b<-fromJSON(parameters)
b["ReferenceValue"]=i
r <- POST(url, body = parameters,encode = "json")
r_c<-toJSON(content(r))
print(r_c)
}
}
)
让数据帧在 Shiny 应用程序中使用的所有环境中持久存在的一种简单方法是使用“<<-”分配而不是“<-”分配。这不是一个很好的编程技术,但它可能是你希望找到什么。
# To get a data frame to persist, use
a <<- b
# instead of
a <- b
**更新答案**
根据您更新的答案,我会将您的 API 调用包装到一个observeEvent
中,一旦按下操作按钮就会触发。 由于您没有提供带有一些真实代码的工作示例,因此我不确定下面的示例是否有帮助。 我进一步假设您的for loop
是正确的并且可以正常工作(就我而言,如果没有真正的 API 和一些实际值,我无法知道)。
library(dplyr)
library(shiny)
library(httr)
library(jsonlite)
shinyApp(ui = fluidPage(
selectInput(inputId = "cyl",
label = "Number cylinders:",
choices = c("all",sort(unique(mtcars$cyl))),
selected = "all"),
actionButton("capture",
"capture value")
), # closes fluidPage
server = function(input, output) {
# some example reactive data
cars_react <- reactive({
mtcars %>%
filter(cyl == input$cyl | input$cyl == "all")
})
# here we access the reactive data with isolate and make it non-reactive, but can update the values through a button click
observeEvent(input$capture, {
for (i in unique(cars_react()$hp))
{
url = "https://oscar.com/prweb/PRRestService/"
parameters<-'{
"Reference":"Account"
,"ReferenceValue":""
}'
b<-fromJSON(parameters)
b["ReferenceValue"]=i
r <- POST(url, body = parameters,encode = "json")
r_c<-toJSON(content(r))
print(r_c)
}
})
}
)
旧答案
从你的问题中不清楚你想如何、在哪里以及多久使用你的反应数据框的向量。 但这是一个重要的问题,因为当您来自纯非反应性 R 环境时,很难掌握反应性的概念以及如何访问它。
下面是一个简单的示例应用程序,它展示了如何访问响应式数据帧中的向量,以及如何使用它们。
我希望它有助于更好地理解 shiny 中的反应性。
library(dplyr)
library(shiny)
shinyApp(ui = fluidPage(
sidebarLayout(
sidebarPanel(
selectInput(inputId = "cyl",
label = "Number cylinders:",
choices = c("all",sort(unique(mtcars$cyl))),
selected = "all"),
actionButton("capture",
"capture value")
), # closes sidebarPanel
mainPanel(
tableOutput("text"),
tableOutput("text2"),
tableOutput("text3"),
tableOutput("table")
) # closes mainPanel
) # closes sidebarLayout
), # closes fluidPage
server = function(input, output) {
# some example reactive data
cars_react <- reactive({
mtcars %>%
filter(cyl == input$cyl | input$cyl == "all")
})
# simply global assignment of a reactive vector
observeEvent(cars_react(), {
# here is a globally assigned vector taken from the reactive data
# reused in a render statement it will not react to change, since it is not reactive
test_vec3 <<- unique(cars_react()$hp)
})
# here a file is written to the working directory of your shiny app
# everytime cars_react() changes write (and overwrite) vector to a file
observeEvent(cars_react(), {
test_vec = unique(cars_react()$hp)
saveRDS(test_vec, file = "test_vec.Rdata")
})
# same as above but the file is gradually growing and not overwritten
# everytime cars_react() changes add vector to a (over several sessions growing) list
observeEvent(cars_react(), {
test_vec2 = unique(cars_react()$hp)
if (file.exists("test_list.Rdata")) {
temp = readRDS("test_list.Rdata")
test_list = c(temp, list(test_vec2))
} else {
test_list = list(test_vec2)
}
saveRDS(test_list, file = "test_list.Rdata")
})
# here we access the reactive data with isolate and make it non-reactive, but can update the values through a button click
text_vec <- eventReactive(input$capture, {
isolate(unique(cars_react()$hp))
})
# output of our reactive data as table
output$table <- renderTable({
cars_react()
})
# text output of globally assigned non-reactive vector test_vec3 (not changing!)
output$text <- renderText({
test_vec3
})
# you can capture values of reactives with isolate, but then, they don't change anymore
# text output of isolated formely reactive vector unique(cars_react()$hp (not changing!)
output$text2 <- renderText({
isolate(unique(cars_react()$hp))
})
# text output of new reactive vector (changes when input$capture button is clicked)
output$text3 <- renderText({
text_vec()
})
}
)
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