如果我在get_data（）反应式表达式中添加去抖动，则第一次获取数据时不会绘制图。但是，更改数据（通过选择新的mpg）会导致绘制图。为什么是这样？有解决方法吗？
这是一个演示问题的简单示例。尝试删除%>% debounce(500)，看看它是否可以按预期工作：
if (interactive()) {
options(device.ask.default = FALSE)
library(shiny)
library(magrittr)
ui <- fluidPage(
selectInput("select", label = "select mpg", choices = c(mtcars$mpg, ""), selected = ""),
plotOutput("plot")
)
server <- function(input, output, session) {
get_data <- reactive({
req(input$select)
mtcars[mtcars$mpg == input$select,]
}) %>% debounce(500)
get_plot <- reactive({
data <- get_data()
print(data)
plot(get_data())
})
output$plot <- renderPlot({
get_plot()
})
}
shinyApp(ui, server)
}
答案 0 :(得分：0)
这里发生的事情。我认为我们不允许在选择输入中包含重复项。 export class DataService {
constructor(protected http: HttpClient, protected logger: NGXLogger, protected translate: TranslateService) {}
get<T>(id?: string, options?: HttpOptions): Observable<T> {
const caller = findCaller(new Error());
const uriWithId = id ? `/${id}` : '';
const requestUrl = this.addGlobalQueryParams(`${this.url}${uriWithId}`);
this.logger.debug(`DataService - GET method [${caller}] - START - URL:: ${requestUrl}`);
return this.http.get<T>(requestUrl, options).pipe(map((response: any) => {
this.logger.debug(`DataService - GET method [${caller}] - END - URL:: ${requestUrl} - Response:: `, response);
return response;
}));
}
getAll<T>(url?: string, options?: HttpOptions): Observable<T> {
const caller = findCaller(new Error());
if (url) {
this.logger.debug(`DataService - POST method [${caller}] - START - URL:: `, url);
return this.http.post<T>(url).pipe(map((response: any) => {
this.logger.debug(`DataService - POST method [${caller}] - END - URL:: ${url} - Response:: `, response);
return response;
}));
}
}
}
中包含重复的值。将初始值设置为mtcars$mpg也会引起奇怪的行为。如果您确实希望初始图连同去抖动一起为空，则可以将其设置为""。这就是它的样子。
" "否则，如果您可以进行初始绘图，可以进行以下工作。注意使用if (interactive()) {
options(device.ask.default = FALSE)
library(shiny)
library(magrittr)
ui <- fluidPage(
selectInput("select", label = "select mpg", choices = c(" ",unique(mtcars$mpg)),selected = " "),
plotOutput("plot")
)
server <- function(input, output, session) {
get_data <- reactive({
req(input$select)
if(!is.na(as.numeric(input$select))) mtcars[mtcars$mpg == input$select,] else NULL
}) %>% debounce(500)
get_plot <- reactive({
req(get_data())
data <- get_data()
print(data)
plot(get_data())
})
output$plot <- renderPlot({
get_plot()
})
}
shinyApp(ui, server)
}
unique()我什至尝试用if (interactive()) {
options(device.ask.default = FALSE)
library(shiny)
library(magrittr)
ui <- fluidPage(
selectInput("select", label = "select mpg", unique(mtcars$mpg)),
plotOutput("plot")
)
server <- function(input, output, session) {
get_data <- reactive({
req(input$select)
mtcars[mtcars$mpg == input$select,]
}) %>% debounce(500)
get_plot <- reactive({
req(get_data())
data <- get_data()
print(data)
plot(get_data())
})
output$plot <- renderPlot({
get_plot()
})
}
shinyApp(ui, server)
}
替换选择输入。这仍然引起问题。