r - Shiny :将 input$var 传递给 ggplot2 中的 aes()

Question

我正在尝试编写一个 Shiny 应用程序，按年龄 (AGE) 或性别 (SEX) 类别绘制变量 VAL 的密度图。用户在下拉菜单中选择“SEX”或“AGE”，我一直在尝试使用fill = input$Group_select在 ggplot 和 ggvis 中。

在 ggplot 中:

output$plot <- renderPlot(ggplot(gdat[gdat$GFR==input$GFR_select,]) + 
                      aes(x= VAL, fill=input$Group_select) +
                      geom_density(adjust=input$slider1))

编辑:正如docendo所指出的，这可以使用aes_string修复ggplot:

output$plot <- renderPlot(ggplot(gdat[gdat$GFR==input$GFR_select,]) + 
                              aes(x= VAL) +
                              geom_density(adjust=input$slider1, aes_string(fill=input$Group_select))): 

在 ggvis 中:

gvis <- reactive(subset(gdat, GFR==input$GFR_select) %>% 
                 ggvis(x = ~VAL) %>% group_by_(input$Group_select) %>%
                 layer_densities(adjust = input$slider1) %>%
                 add_axis("y", title = "Density", ticks="none") %>%
                 scale_numeric("x", domain = c(0, 230)) ) 
gvis %>% bind_shiny("ggvis", "ggvis_ui")

解决方案:使用 as.name(input$Group_select) 将正确呈现图形!

这是(曾经)呈现的内容: Imgur link to shiny output .有趣的是，group_by_ 似乎正确地解释了 input$Group_select，而 input$Group_select 被视为 fill=input$Group_select 中的常量。

关于如何使绘图正确渲染的任何想法？

这是完整的 Shiny 代码:

用户界面

library(shiny)
library(ggplot2)
library(dplyr)
library(ggvis)
shinyUI(fluidPage(
  titlePanel("eGFR in the ARIC study"),
  sidebarPanel(
    selectInput("Group_select",
                label=h3("By-Variable"),
                choices=c("AGE","SEX","ALL"),
                selected="SEX"),
    selectInput("GFR_select",
                label=h3("Creatinine Measure"),
                choices=c("BOTH", "CREATININE", "CYSTATIN", "MDRD"),
                selected="MDRD"),
    sliderInput("slider1", label = h3("Bandwith Adjustment"),
                min = 0.5, max = 4, value = 1)
  ),
  mainPanel(
    uiOutput("ggvis_ui"),
    ggvisOutput("ggvis"),
    plotOutput("plot")
  )
))

服务器

library(shiny)
source("helpers.R")
shinyServer(function(input, output) {
  gvis <- reactive(subset(gdat, GFR==input$GFR_select) %>% 
                     ggvis(x = ~VAL, fill = ~input$Group_select) %>% group_by_(input$Group_select) %>%
                     layer_densities(adjust = input$slider1) %>%
                     add_axis("y", title = "Density", ticks="none") %>%
                     scale_numeric("x", domain = c(0, 230)) ) 
  gvis %>% bind_shiny("ggvis", "ggvis_ui")
  output$plot <- renderPlot(ggplot(gdat[gdat$GFR==input$GFR_select,]) + 
                          aes(x= VAL, fill=input$Group_select) +


      geom_density(adjust=input$slider1))
})

Answer 1

我不确定这仍然是一个悬而未决的问题，但可以替代 aes_string将字符串转换为符号:

library(ggplot2)

# usually you can put all the shared aesthetics in the first line
ggplot(mtcars, aes(mpg, hp, colour = cyl)) +
  geom_point()

# when the input is a string, you can use aes_string(), but you'd
# have to enter the string var separately, or change all vars..

input <- "cyl"

ggplot(mtcars, aes(mpg, hp)) +
  geom_point(aes_string(colour = input))

# or
# ggplot(mtcars, aes_string("mpg", "hp", colour = input)) +
#  geom_point()

# you can put the converted string var in the normal aes()
ggplot(mtcars, aes(mpg, hp, colour = !!as.symbol(input))) +
  geom_point()

# note: as.name() and as.symbol() are aliases

创建于 2018-11-05 由 reprex package (v0.2.0)。