eval的错误(expr, envir, enclos):对象的输入没有找到。

I'm trying to allow the user to select which column of data (selecty) they would like to make a plot of. Everything else in my app works except for this part. Here are the relevant portions of my code:

我正在尝试让用户选择他们想要绘制的数据列(selecty)。除了这个部分，我的应用程序中其他的东西都是有用的。以下是我的代码的相关部分:

#ui.R

library(shiny)
library(ggplot2)
shinyUI(fluidPage(h1("Title 1"),
              # Sidebar
              sidebarLayout(
                sidebarPanel(
                  h3("Title 2"),
                  selectInput("pnum",
                              label = "Select the patient number",
                              choices = unique(pnums), selected = pnums[1]),
                  selectInput("selecty",
                              label = "Choose a variable to display on the     y-axis",
                              choices = list('Var1', 'Var2', 'Var3', 'Var4')),
                  dateRangeInput("dates", label= "Date Range"),
                  submitButton("Create Graph")
                ),
                # Show a plot
                mainPanel(
                  plotOutput('makeplot')
              )
)
))

#server.R
#relevant portion only - ggplot

library(shiny)
require(RODBC)
library(ggplot2)
library(quantmod)
library(reshape)

shinyServer(function(input, output) {

output$makeplot <- renderPlot({

p <- ggplot(pdata(), aes(x = Time_Stamp, y = input$yselect)) + geom_point()

print(p)
})
})

The data is brought from an online database and is a reactive function. My main issue is that in the user select for the column, it has to be in single quotes, although I would like to transfer it over to the ggplot function without the quotes so it acts as the column name. I've also tried to make a switch statement within the 'y = ' but I get the same error.

数据来自一个在线数据库，是一个反应性的函数。我的主要问题是，在用户选择的列中，它必须在单引号中，尽管我想把它转换到没有引号的ggplot函数，所以它充当列名。我还尝试在“y =”中做一个switch语句，但是我得到了相同的错误。

1 个解决方案

#1

First, in your ggplot call, you should have y = input$selectyto be consistent with your naming in ui.R.

首先，在您的ggplot调用中，您应该有y =输入$selectyto与您在ui.R中的命名一致。

Then, if I understood correctly, you should take a look at the aes_string function in ggplot because aes uses non-standard evaluation which allows you to specify variable names directly and not as characters. Here, input$yselect is passed as a character so you need to replace in server.R :

然后，如果我理解正确，您应该看一下ggplot中的aes_string函数，因为aes使用非标准的评估，它允许您直接指定变量名，而不是作为字符。在这里，输入$yselect作为字符传递，因此您需要在服务器中替换。接待员:

p <- ggplot(pdata(), aes(x = Time_Stamp, y = input$yselect)) + geom_point()

with

与

p <- ggplot(pdata(), aes_string(x = "Time_Stamp", y = input$selecty)) + geom_point()