我尝试过（徒劳）在Rmarkdown中使用ggplot生成一个图表。代码如下：

```{r,echo=FALSE}
#fig.width=12,fig.height=6
panel2$PlotSize<-round(log(panel2$BSFA0200),0)- min(round(log(panel2$BSFA0200),0))+1# set size of dots
panel2$PlotSize[panel2$PlotSize==-Inf]<-NA
panel2$PlotColour<-ifelse(panel2$PlotSize<7,1,panel2$PlotSize)
panel2$PlotSize<-as.factor(panel2$PlotSize)
panel2$PlotColour<-as.factor(panel2$PlotColour)

g1<-ggplot(data=panel2,aes(x=NFR,y=PROF7*100,size=PlotSize,colour=PlotSize))+ geom_point()

g1

在编结这工程罚款，但当执行一个Rmd文件（无论是作为html或pdf）我总是得到这个错误消息

processing file: 1Profti_model.Rmd
|.. | 4%
ordinary text without R code

|..... | 8%
label: setup (with options)
List of 1
$ include: logi FALSE

|........ | 12%
ordinary text without R code

|.......... | 15%
label: unnamed-chunk-1 (with options)
List of 3
$ echo : logi FALSE
$ warning: logi FALSE
$ message: logi FALSE

Attaching package: 'dplyr'

The following objects are masked from 'package:stats':

filter, lag

The following objects are masked from 'package:base':

intersect, setdiff, setequal, union

Loading required package: zoo

Attaching package: 'zoo'

The following objects are masked from 'package:base':

as.Date, as.Date.numeric

|............ | 19%
inline R code fragments

|............... | 23%
label: unnamed-chunk-2 (with options)
List of 1
$ echo: logi FALSE

|.................. | 27%
ordinary text without R code

|.................... | 31%
label: unnamed-chunk-3 (with options)
List of 1
$ echo: logi FALSE

Quitting from lines 98-109 (1Profti_model.Rmd)
Error in png(..., res = dpi, units = "in") : unable to start png() device
Calls: ... in_dir -> plot2dev -> do.call -> -> png
In addition: Warning messages:
1: Removed 55 rows containing missing values (geom_point).
2: In png(..., res = dpi, units = "in") :
unable to open file '1Profti_model_files/figure-html/unnamed-chunk-3-1.png' for writing
3: In png(..., res = dpi, units = "in") : opening device failed

Execution halted

我也试着解决这个问题，将图表保存在png中，然后将其作为图片加载。也没有结果（参见[Error with loading png in Rmd file](https://stackoverflow.com/questions/34136738/error-with-loading-png-in-rmd-file)）
谢谢你的帮忙
更新：
根据你们中一些人的建议，我添加了一个不同的块名，并在我的数据上复制了Davit的代码（见更新的代码）。不幸的是，错误仍然存在。有趣的是，knitr不能写png，但可以在代码所在的同一个文件夹中写csv（我测试了它）。
最后，我测试了在我的C驱动器上运行同样的代码，（惊喜！）它工作正常。然而，这对我来说不是很有效，因为我不想依赖于特定的机器，我需要与其他人分享这项工作（所以网络驱动器是必须的）。此外，所有其他包/代码在网络驱动器上都能正常工作，只有这个png（）似乎是一个问题。
谢谢你的帮助！---标题：新文档作者：我的输出：html_document ---

#.libPaths("D:/xxxx/packages")
require(ggplot2)

 panel2 <- data.frame(BSFA0200 = rnorm(100),
                        NFR = rnorm(100),
                        PROF7 = rnorm(100))

panel2$PlotSize<-round(log(panel2$BSFA0200),0)- min(round(log(panel2$BSFA0200),0))+1# set size of dots
panel2$PlotSize[panel2$PlotSize==-Inf]<-NA
panel2$PlotColour<-ifelse(panel2$PlotSize<7,2,panel2$PlotSize)

write.csv(panel2[1:100,c('BSFA0200',"NFR","PROF7")],file="test.csv")

g1 <- ggplot(data = panel2,
             aes(x = NFR,
                 y = PROF7 * 100,
                 size = factor(PlotSize),
                 colour = factor(PlotSize)
                 ))

g1 + geom_point()

错误输出：

Loading required package: ggplot2

Quitting from lines 9-32 (test.Rmd)
Error in png(..., res = dpi, units = "in") : unable to start png() device
Calls: ... in_dir -> plot2dev -> do.call -> -> png
In addition: Warning messages:
1: Removed 35 rows containing missing values (geom_point).
2: In png(..., res = dpi, units = "in") :
unable to open file 'test_files/figure-html/prova-1.png' for writing
3: In png(..., res = dpi, units = "in") : opening device failed
Execution halted

我的knitr版本是1.11（应该是最新的），R版本是3.2.2

R.Version()
$platform
[1] "i386-w64-mingw32"

$arch
[1] "i386"

$os
[1] "mingw32"

$system
[1] "i386, mingw32"

$status
[1] ""

$major
[1] "3"

$minor
[1] "2.2"

$year
[1] "2015"

$month
[1] "08"

$day
[1] "14"

$svn rev
[1] "69053"

$language
[1] "R"

$version.string
[1] "R version 3.2.2 (2015-08-14)"

$nickname
[1] "Fire Safety"