您可以使用cat()将markdown嵌入循环中.

You can embed the markdown inside the loop using cat().

注意:您需要将results="asis"设置为要呈现为markdown的文本. 请注意:在\n换行符前面需要两个空格，以使knitr在存在绘图的情况下正确渲染减价.

Note: you will need to set results="asis" for the text to be rendered as markdown. Note well: you will need two spaces in front of the \n new line character to get knitr to properly render the markdown in the presence of a plot out.

# Monthly Air Quality Graphs
```{r pressure,fig.width=6,echo=FALSE,message=FALSE,results="asis"}

attach(airquality)
for(i in unique(Month)) {
  cat("  \n###",  month.name[i], "Air Quaility  \n")
  #print(plot(airquality[airquality$Month == i,]))
  plot(airquality[airquality$Month == i,])
  cat("  \n")
}
```