使用for循环中的ggplot绘图不能编译为PDF

Question

我使用knitR（.Rnw）创建了一个报告，将其编译为PDF。由于我想为每个问题绘制相同的数字，我在for循环中创建了一个图。不幸的是，我在PDF中收到警告并且没有真正得到导致错误的原因...

这是我认为问题开始的块：循环在R中运行良好但不编译为PDF（参见下面的完整代码）。我尝试了各种标签，打印功能和其他东西，但无法找到解决方案。

<<echo=FALSE, warning=T, message=F>>=

for(i in 1:3){
  cat(paste("\subsection{",titel[i],"}
", sep=""))
  cat(paste("Figure \ref{class",i,"} 
", sep=""))
   cat(paste("\begin{figure}[H] 
", sep=""))
   cat(paste("\begin{center} 
", sep=""))
     cat(paste("\includegraphics[width=1\textwidth,", 
            "height=.47\textheight,keepaspectratio]{class",i,".pdf}\caption{",titel[i],"}
", sep=""))

    cat(paste("\label{class",i,"}" 
, sep=""))
    cat(paste("\end{center} 
",sep=""))
  cat(paste("\end{figure} 
",sep=""))



  p <- ggplot(data[!is.na(data$F17),], aes_string(x=Fragen[i], y="..prop..", group = "1", fill="F17"))+ 
       geom_bar()+
       facet_grid(F17~.)+
       geom_text(aes(label = scales::percent(..prop..),
              y= ..prop.. ), stat= "count", vjust = -.5, size=3) + 
       ylab("Prozent")+
       xlab(titel[i])+
       scale_fill_manual(name="Individuals", values=colorScheme)#+
       #theme_mine


 pdfnam<-paste("class",i,".pdf",sep="") #produce a plot for each class
 pdf(file=pdfnam,width=12, height = 4)
 #gridExtra::grid.arrange(p, q)
 print(p)
 dev.off()
}

@

这是复制的完整代码：

documentclass{article}

usepackage{amsmath,amssymb,amstext}
usepackage{graphicx}
usepackage{geometry}
geometry{top=15mm, left=25mm, right=25mm, bottom=25mm,headsep=10mm,footskip=10mm} 
usepackage{xcolor}
usepackage{float}
usepackage[T1]{fontenc} % Umlaute
usepackage[utf8]{inputenc}
inputencoding{latin1}

egin{document}
parindent 0pt

	itle{title} 
maketitle

<<echo=FALSE, warning=FALSE, message=FALSE>>=
library(ggplot2)
library(reshape)
library(knitr)
library(doBy)
library(dplyr)


opts_chunk$set(fig.path='figure/graphic-', fig.align='center', fig.show='hold',fig.pos='!ht',
           echo=FALSE,warning = FALSE) 

@

 <<echo=FALSE, warning=FALSE, message=F>>=

 # data and other useful stuff

 data <- data.frame(F1 = c("A", "A", "B", "C"), # answers to question 1, ...
                    F2 = c("A", "B", "B", "C"),
                    F3 = c("A", "B", "C", "C"),
                    F17 = c("K", "L", "L", "M")) # K, L and M are a certain individual. L answered twice.

 # colour scheme:
 GH="#0085CA"; H="#DA291C"; BV="#44697D"
 colorScheme <- c(BV, H, GH)

 # individual theme for plots:
theme_mine = theme(plot.background = element_rect(fill = "white"),
               panel.background = element_rect(fill = "white", colour = "grey50"),
               text=element_text(size=10, family="Trebuchet MS"))

# a vector with the variable names from "data" (F1, F2, F3).
Fragen <- c(paste0('F',seq(1:3), sep=""))

# question title for labeling the plots:
titel <- c("Q1", "Q2", "Q3", "Q17")

@


egin{figure}[h]
egin{center}
<<echo=FALSE, fig.width=9.6, fig.height=6, warning=FALSE>>=

p <- ggplot(data, aes(x=F17))+
     geom_bar(fill = colorScheme)+
     xlab(titel[4])+
     #geom_text(aes(label = scales::percent(..prop..),
     #          y= ..prop.. ), stat= "count", vjust = -.5, size=3) + 
     ylab("Absolut")+
     theme_bw()
     #theme_mine   # does not work properly yet.
p

@
caption{figa}
label{figa}
end{center}
end{figure}

section{individual plots}

<<echo=FALSE, warning=T, message=F>>=

# here is where the problem starts: the loop runs fine within R but does not compile to an PDF.

for(i in 1:3){
  cat(paste("\subsection{",titel[i],"}
", sep=""))
  cat(paste("Figure \ref{class",i,"} 
", sep=""))
   cat(paste("\begin{figure}[H] 
", sep=""))
   cat(paste("\begin{center} 
", sep=""))
     cat(paste("\includegraphics[width=1\textwidth,", 
            "height=.47\textheight,keepaspectratio]{class",i,".pdf}\caption{",titel[i],"}
", sep=""))

    cat(paste("\label{class",i,"}" 
, sep=""))
    cat(paste("\end{center} 
",sep=""))
  cat(paste("\end{figure} 
",sep=""))



  p <- ggplot(data[!is.na(data$F17),], aes_string(x=Fragen[i], y="..prop..", group = "1", fill="F17"))+ 
       geom_bar()+
       facet_grid(F17~.)+
       geom_text(aes(label = scales::percent(..prop..),
              y= ..prop.. ), stat= "count", vjust = -.5, size=3) + 
       ylab("Prozent")+
       xlab(titel[i])+
       scale_fill_manual(name="Individuals", values=colorScheme)#+
       #theme_mine


 pdfnam<-paste("class",i,".pdf",sep="") #produce a plot for each class
 pdf(file=pdfnam,width=12, height = 4)
 #gridExtra::grid.arrange(p, q)
 print(p)
 dev.off()
}

@


end{document}

非常感谢提前！