R shiny：使用通过 ui 获得的字符串在绘图标题中表达方程式

Question

我写了下面的r代码：

remove(list = ls())
library(shiny)
library(ggplot2)

ui <- pageWithSidebar(
  headerPanel('Plot a function'),
  sidebarPanel(
    textInput("func", "Function to plot:", value = "x"),
    numericInput("xMin", "Set the minimum of x: ", value = 0),
    numericInput("xMax", "Set the maximum of x: ", value = 10),
    submitButton("Plot")
  ),
  mainPanel(plotOutput("plot"))
)

server <- function(input, output) {
  output$plot <- renderPlot({
    x <- seq(input$xMin, input$xMax, 0.01)
    f <- function(x) {
      eval(parse(text = input$func))
    }
    y <- f(x)
    df <- data.frame(x, y)
    theme_set(theme_bw(base_size = 12))
    figure <- ggplot(df, aes(x, y)) +
      geom_line() +
      labs(x = "x",
           y = "y",
           title = parse(text = input$func)) +
      theme(plot.margin = unit(c(.6, .6, .6, .6), "cm"),
            plot.title = element_text(hjust = 0.5))
    plot(figure)
    filename <- "plotFunction.jpeg"
    ggsave(filename,
           width = 6,
           height = 4,
           dpi = 200)
  })
}

shinyApp(ui = ui, server = server)

当用户输入x^2 - 2指定函数时，我得到如下输出：

Output of the code

我想让剧情标题以y =开头（这样整个标题会变成y = x^2 - 2，x^2渲染正确），但是我一直做不到所以。例如，如果我将用户输入字符串与 y = 连接起来，标题将变为 (= y, x^2 - 2)（尽管 x^2 已正确呈现）。

Answer 1

你可以这样做：

labs(title = parse(text=paste0("y == ", input$func)))

R shiny：使用通过 ui 获得的字符串在绘图标题中表达方程式

R shiny: expressing an equation in a plot title using a string obtained by ui

plot

equation

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title

shiny