我正在建立我的第一个Shiny应用程序，目的是创建抵押计算器和可调整的amoritization时间表。我能够获取以下代码以使用runApp()进行渲染，但它不起作用(即，不输出任何值，也不显示图形)。此外，它在RStudio的控制台中生成以下错误:
“.getReactiveEnvironment()$ currentContext()中的错误:
如果没有事件的响应上下文，则不允许进行操作。 (您尝试做只能从响应式(Reactive)表达式或观察器内部完成的操作。)”
对于背景，我正在运行:
Win 7，64位操作系统| R v3.1.1 |的RStudio v0.98.944
并尝试实现此处定义的过程，但是没有运气:
Shiny Tutorial Error in R
R Shiny - Numeric Input without Selectors
用户界面
library(shiny)
shinyUI(
pageWithSidebar(
headerPanel(
h1('Amoritization Simulator for Home Mortgages'),
windowTitle = "Amoritization Simulator"
),
sidebarPanel(
h3('Mortgage Information'),
h4('Purchase Price'),
p('Enter the total sale price of the home'),
textInput('price', "Sale Price ($USD)", value = ""),
h4('Percent Down Payment'),
p('Use the slider to select the percent of the purchase price you
intend to pay as a down payment at the time of purchase'),
sliderInput('per.down', "% Down Payment", value = 20, min = 0, max = 30, step = 1),
h4('Interest Rate (APR)'),
p('Use the slider to select the interest rate of the loan expressed
as an Annual Percentage Rate (APR)'),
sliderInput('apr', "APR", value = 4, min = 0, max = 8, step = 0.125),
h4('Term Length (Years)'),
p('Use the buttons to define the term of the loan'),
radioButtons('term', "Loan Term (Years)", choices = c(15, 30), selected = 30),
submitButton('Calculate')
),
mainPanel(
h3('Payment and Amoritization Simulation'),
p('Use this tool to determine your monthly mortgage payment,
how much interest you will owe over the life of the loan, and how
you can reduce that amount with additional payment'),
h4('Monthly Payment (Principal and Interest)'),
p('This is the amount (in $USD) you would pay each month for a
mortgage under the terms you defined'),
verbatimTextOutput("base.monthly.payment"),
h4('Total Interest Over Life of Loan'),
p('If paying just that amount per month, this is the total amount
in $USD you will spend on interest for that loan'),
verbatimTextOutput("base.total.interest"),
h4('Additional Principal Simulation'),
p('One way to reduce the interest expense is to pay more principal
each month. Use the slider below to select an additional amount to
include with your payment and see the reduction in interest expense
for the life of the loan.'),
sliderInput('add', "Additional Principal ($USD)", value = 250, min = 0, max = 1000, step = 25),
p('Interest costs saved with this additional principal (in $USD)'),
verbatimTextOutput("savings"),
p('You will also pay the loan off the loan this many months early'),
verbatimTextOutput("early"),
plotOutput('plot')
)
)
)
服务器
library(shiny)
library(ggplot2)
library(scales)
shinyServer(
function(input, output) {
## determine baseline payment and interest total
price <- reactive({as.numeric(input$price)})
per.down <- reactive({input$per.down / 100})
int <- reactive({input$apr / 1200})
n <- reactive({input$term * 12})
base.monthly.payment <- (int() * price() * (1 - per.down()) * ((1 + int())^n())) / (((1 + int())^n()) - 1)
output$base.monthly.payment <- renderPrint({base.monthly.payment})
base.total.interest <- (base.monthly.payment * n()) - (price() * (1 - per.down()))
output$base.total.interest <- renderPrint({base.total.interest})
## create dataframe to populate with increments of additional payment
schedule <- data.frame(matrix(data = NA, nrow = 41, ncol = 6,
dimnames = list(1:41, c("add", "add.n",
"prin", "add.total.interest",
"savings", "early"))))
## initialize 'for' loop to populate possible amoritization totals
c <- 1
for (i in seq(0, 1000, 25)) {
schedule$add[c] <- i
schedule$add.n[c] <- log(((base.monthly.payment + i) / int()) / (((base.monthly.payment + i) / int()) - (price() * (1 - per.down())))) / log(1 + int())
schedule$prin[c] <- round(price() * (1 - per.down()), digits = 2)
schedule$add.total.interest[c] <- round(((base.monthly.payment + i) * schedule$add.n[c]) - schedule$prin[c], digits = 2)
schedule$savings[c] <- round(base.total.interest - schedule$add.total.interest[c], digits = 2)
schedule$early[c] <- round(n() - schedule$add.n[c], digits = 0)
c <- c + 1
}
add <- reactive({input$add})
output$savings <- renderPrint({schedule$savings[which(schedule$add == add())]})
output$early <- renderPrint({schedule$early[which(schedule$add == add())]})
## create data.frame suitable for plotting
graph.data <- data.frame(matrix(data = NA, nrow = 82, ncol = 3,
dimnames = list(1:82, c("add", "amount", "type"))))
c <- 1
for (i in seq(0, 1000, 25)) {
graph.data$add[c] <- i
graph.data$add[c + 1] <- i
graph.data$amount[c] <- schedule$prin[which(schedule$add == i)]
graph.data$amount[c + 1] <- schedule$add.total.interest[which(schedule$add == i)]
graph.data$type[c] <- "Principal"
graph.data$type[c + 1] <- "Interest"
c <- c + 2
}
## create plot of amoritization with line for additional principal amount
output$plot <- renderPlot({
ggplot(graph.data, aes(x = add, y = amount), color = type)
+ geom_area(aes(fill = type), position = 'stack', alpha = 0.75)
+ geom_vline(xintercept = add(), color="black", linetype = "longdash", size = 1)
+ labs(x = "Additional Principal/Month", y = "Total Cost")
+ scale_fill_manual(values=c("firebrick3", "dodgerblue3"), name = "Payment Component")
+ theme(axis.title.x = element_text(face = "bold", vjust = -0.7, size = 16),
axis.title.y = element_text(face = "bold", vjust = 2, size = 16),
axis.text.x = element_text(size = 14),
axis.text.y = element_text(size = 14),
panel.margin = unit(c(5, 5, 5, 5), "mm"),
plot.margin = unit(c(5, 5, 5, 5), "mm"),
panel.background = element_blank(),
panel.grid.major.y = element_line(colour = "gray"),
panel.grid.minor.y = element_line(colour = "gray86"),
panel.grid.major.x = element_blank(),
panel.grid.minor.x = element_blank())
+ scale_x_continuous(labels = dollar)
+ scale_y_continuous(labels = dollar)
})
})
在此先感谢您的帮助!
最佳答案
您的错误如下所示:
base.monthly.payment <- (int() * price() * (1 - per.down()) *
((1 + int())^n())) / (((1 + int())^n()) - 1)
base.monthly.payment利用了均为 react 性的int()，n()，per.down()和price()。因此，base.monthly.payment也将是 react 性的。因此，在创建/分配值时，您需要将其包装在reactive中，如下所示:base.monthly.payment <- reactive ({
(int() * price() * (1 - per.down()) * ((1 + int())^n())) / (((1 + int())^n()) - 1)
})
并像
base.monthly.payment()，n()等一样将其称为int()。对于代码中的许多其他对象也是如此，例如:
schedule，base.total.interest，graph.data。关于R Shiny : Reactive Error，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/26454609/