r - 编织时 Markdown 找不到参数

Question

当我尝试编写以下文档时

----
title: "jerHW52"
output: html_document
params:
  missiontype: "Successful.Unmanned"
---

```{r warning=FALSE,echo=FALSE}
knitr::opts_chunk$set(echo=FALSE)
library(tidyr)
library(ggplot2)
Launch_Data<-read.csv("NASA_Launch_Data.csv",header=TRUE)
NASA_Launch_Data<- Launch_Data %>% filter(Launch_Data$Type==params$missiontype)
ggplot(NASA_Launch_Data, aes(x=Year, y=Missions)) + geom_line() 
```

出现以下错误

Error in filter(., Launch_Data$Type == params$missiontype) : object 'params' not found Calls: ... _fseq -> freduce -> withVisible -> -> filter Execution halted

为什么找不到参数？

这是 NASA_Launch_Data.csv 中数据的开始

"","Year","Type","Missions"
"1",1957,"Successful.Unmanned",3
"2",1958,"Successful.Unmanned",28
"3",1959,"Successful.Unmanned",23
"4",1960,"Successful.Unmanned",40
"5",1961,"Successful.Unmanned",48
"6",1962,"Successful.Unmanned",76
"7",1963,"Successful.Unmanned",67
"8",1964,"Successful.Unmanned",99
"9",1965,"Successful.Unmanned",119
"10",1966,"Successful.Unmanned",129

Answer 1

答案是我是个白痴....

注意我文档顶部的 YAML header

----
title: "jerHW52"
output: html_document
params:
  missiontype: "Successful.Unmanned"
---

第一行有四个破折号，而不是应该的三个。删除一个，一切正常......