Shiny flexdashboard 中的 facet_grid 给出错误“构面变量必须至少有一个值”
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【中文标题】Shiny flexdashboard 中的 facet_grid 给出错误“构面变量必须至少有一个值”【英文标题】:facet_grid in Shiny flexdashboard giving error "Faceting variables must have at least one value" 【发布时间】:2018-12-27 20:37:52 【问题描述】:我在让 ggplot2 facet_grid
绘图为评估系统工作时遇到了一些麻烦。情节渲染良好,但我在浏览器和控制台中收到以下错误:
错误:分面变量必须至少有一个值
每次我根据输入 input$brand
切换品牌条目时都会发生这种情况。应用程序不会崩溃,但错误消息很烦人。
我准备了这个可重现的例子:
---
title: "Power ranking for mtcars"
runtime: shiny
output:
flexdashboard::flex_dashboard:
orientation: rows
source_code: embed
---
```r rows.print = 25
library(dplyr)
library(ggplot2)
mtcars_tidy <- mtcars %>%
tibble::rownames_to_column() %>%
rename(model = rowname) %>%
mutate(brand = gsub( " .*$", "", model )) %>%
mutate(model = model) %>%
select(brand, model, everything()) %>%
tidyr::gather(key = 'measure', value = "value", mpg:carb) %>%
mutate(ranking = as.factor(sample(x = c(1, 2, 3), size = n(), replace = TRUE))) %>%
mutate(power = case_when(
.$measure == "hp" & value > 200 | (.$measure == "cyl" & value == 8) ~ "high",
.$measure == "hp" & value < 200 | (.$measure == "cyl" & value == 8) ~ "medium",
.$measure == "hp" & value > 100 | (.$measure == "cyl" & value == 6) ~ "high",
.$measure == "hp" & value < 100 | (.$measure == "cyl" & value == 6) ~ "medium",
.$measure == "hp" & value > 50 | (.$measure == "cyl" & value == 6) ~ "high",
.$measure == "hp" & value < 50 | (.$measure == "cyl" & value == 6) ~ "medium",
.$measure == "hp" & value > 200 | (.$measure == "carb" & value > 4) ~ "high",
.$measure == "hp" & value < 200 | (.$measure == "carb" & value <= 4) ~ "medium",
.$measure == "hp" & value > 100 | (.$measure == "carb" & value > 2.8) ~ "high",
.$measure == "hp" & value < 100 | (.$measure == "carb" & value <= 2.8) ~ "medium",
.$measure == "hp" & value > 50 | (.$measure == "carb" & value > 2) ~ "high",
.$measure == "hp" & value < 50 | (.$measure == "carb" & value <= 2) ~ "medium",
TRUE ~ "low"
))
```
# Sidebar .sidebar data-
```r
selectInput("brand", "Brand of the car",
choices = unique(mtcars_tidy$brand))
renderUI(
selectInput("model", "Car model",
choices = mtcars_tidy$model[mtcars_tidy$brand == levels(mtcars_tidy$brand)[1]])
)
br()
observe(
brand <- input$brand
updateSelectInput(session, "model",
choices = mtcars_tidy$model[mtcars_tidy$brand == brand])
)
# when switching the brand of the car, input$brand this error pops up:
# Error in : Faceting variables must have at least one value
```
# Main
##
### Plot power ranking for each measure
```r
nameorder <- make.unique(mtcars_tidy$measure[order(mtcars_tidy$power, mtcars_tidy$ranking)])
mtcars_tidy$measure <- factor(mtcars_tidy$measure, levels=nameorder,
ordered = TRUE)
dataset <- reactive(
subset(mtcars_tidy, brand == input$brand & model == input$model)
)
renderPlot(
ggplot(dataset(), aes(x = ranking, y = measure)) +
geom_segment(aes(yend = measure), xend=0, color = "grey50") +
geom_point(size = 3, aes(colour = power)) +
scale_colour_brewer(palette="Set1", limits = c("high","medium", "low")) +
theme_bw() +
theme(panel.grid.major.y = element_blank()) + # No horizontal grid lines
facet_grid(power ~ ., scales="free_y", space="free_y") +
ggtitle(paste0("Brand: ", input$brand, ", Model: " , input$model))
)
```
编辑 1:我将 facet_grid
更改为 facet_wrap
,但错误仍然存在。
编辑 2:根据建议,我使用以下公式切换到 facet_wrap
:p <- p + facet_wrap(power ~ .)
。还是一样的错误。我也试过这个其他公式
p <- p + facet_wrap(power ~ ranking)
。错误仍然存在。
编辑 3:在 facet_wrap
函数上,我也尝试了这些公式:
facet_wrap(~power )
facet_wrap(vars(power ))
facet_wrap(vars(power , ranking))
。
错误仍然相同(相同)。没有变化 (Error in : Faceting variables must have at least one value
)。
编辑 4:如果我尝试使用 facet_wrap(power)
,错误会更严重,因为这满嘴会导致 Shiny 崩溃:
Error: Column `function (lambda = 1) \n\n if (!is.numeric(lambda) || is.na(lambda)) \n stop("invalid argument 'lambda'")\n if (lambda <= 0) \n return(make.link("log"))\n if (lambda == 1) \n return(make.link("identity"))\n linkfun <- function(mu) mu^lambda\n linkinv <- function(eta) pmax(eta^(1/lambda), .Machine$double.eps)\n mu.eta <- function(eta) pmax((1/lambda) * eta^(1/lambda - \n 1), .Machine$double.eps)\n valideta <- function(eta) all(is.finite(eta)) && all(eta > \n 0)\n link <- paste0("mu^", round(lambda, 3))\n structure(list(linkfun = linkfun, linkinv = linkinv, mu.eta = mu.eta, \n valideta = valideta, name = link), class = "link-glm")\n` must be a 1d atomic vector or a list
【问题讨论】:
试试facet_wrap(~ power, ...)
。您需要将这两个变量都明确指定为facet_grid
。
你也调整了公式吗?
是的,我把它改成了p <- p + facet_wrap(relevance ~ .)
。见编辑。
所以...不。请注意facet_wrap
中没有点。
我也尝试了这些公式:facet_wrap(~power)、facet_wrap(vars(power))、facet_wrap(vars(power,ranking))。错误仍然相同。另一个,facet_wrap(power)
,让 Shiny 崩溃了。请参阅上面的编辑。
【参考方案1】:
当dataset()
中没有行时会发生此错误。当我运行您的代码(当前版本为facet_grid(power ~ .,
)时,它实际上工作正常。当我选择一个新品牌时,它会在input$model
列表更新时显示此错误。一旦完成,brand
和 model
的组合返回行,该图就会很好地显示。
您可以通过使用req
推迟绘制绘图直到满足某些要求来防止这种差距。只需在 renderPlot
顶部插入以下代码
req(nrow(dataset()) > 0)
如果dataset()
不包含至少一行,这将阻止renderPlot
运行。在这种情况下,在数据准备好使用之前,绘图将是空白的(删除可怕的错误消息)。添加该行后,您的应用程序似乎运行良好(顺便说一句,看起来相当不错)。
您可以通过在shiny
上下文之外测试您的代码来查看该错误消息的来源。这是您的情节的一个最小示例:
ggplot(dataset, aes(x = ranking, y = measure)) +
geom_segment(aes(yend = measure), xend=0, color = "grey50") +
geom_point(size = 3, aes(colour = power)) +
facet_grid(power ~ ., scales="free_y", space="free_y")
当我使用此电话拨打dataset
时:
dataset <- subset(mtcars_tidy, brand == 'Honda' & model == 'Honda Civic')
情节正确渲染。当我使用不返回任何行的subset
时:
dataset <- subset(mtcars_tidy, brand == 'Honda' & model == 'Civic')
我得到了同样的错误:
Error: Faceting variables must have at least one value
【讨论】:
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