title: Problems passing string with \n to ggtitle
body: <p>I think this might have an easy answer - which I can't seem to find anywhere - so I'll forgo the reproducibility for the moment. I have a function designed to draw a <code>ggplot2</code>. I use <code>mapply</code> to pass it a few vectors of strings for the functions input parameters. The parameter of concern here is <code>title</code>. Which is fed a character vector with elements such as <code>"this is a plot title"</code>.</p>
  
  <p>Then the following code:</p>
  
  <pre><code>p &lt;- ggplot(df, aes(x=date, y=value)) 
  
  ## plot the line 
  p &lt;- p + geom_line()
  
  ## add plot title
  p &lt;- p + ggtitle(title)
  </code></pre>
  
  <p>actually works just fine and the plot title is <code>"this is a plot title"</code> as expected.</p>
  
  <p>However if the title is long and I want to specify a point to wrap the title using <code>\n</code> it fails to work.</p>
  
  <p>Precisely if I feed ggtitle an element of <code>"this is a \n plot title"</code>. I get exactly that contained in the quotes, rather than wrapping the title at the <code>\n</code>. My suspicion is I need <code>eval</code>, or <code>paste</code> or <code>get</code>, but my formations of such a request have failed to achieve the desired results. I appreciate the help. </p>
  
  <p>UPDATE:
  I guess it must be the interaction with mapply. This should allow you to reproduce the problem.</p>
  
  <p>create data.frame of strings as sample and assign it to <code>fred.M.SA</code></p>
  
  <pre><code>  structure(list(RegionalCoverage = c("National", "National", "National", 
    "National", "National", "National"), GeographicLevel = c("MSA", 
    "MSA", "MSA", "MSA", "MSA", "MSA"), Category = c("Workers", "Workers", 
  "Workers", "Workers", "Workers", "Workers"), Sector = c("Labor Market", 
  "Labor Market", "Labor Market", "Labor Market", "Labor Market", 
  "Labor Market"), Source2 = c("FRED", "FRED", "FRED", "FRED", 
  "FRED", "FRED"), Title = c("Unemployment Rate in La Crosse, WI-MN (MSA)", 
  "Trade, Transportation and Utilities Employment in La Crosse, WI-MN (MSA)", 
  "Professional and Business Services Employment in La Crosse, WI-MN (MSA)", 
  "Other Services Employment in La Crosse, WI-MN (MSA)", "Manufacturing Employment in La Crosse, WI-MN (MSA)", 
  "Leisure and Hospitality Employment \\n in La Crosse, WI-MN (MSA)"
  ), SeriesID = c("LACR155UR", "LACR155TRAD", "LACR155PBSV", "LACR155SRVO", 
  "LACR155MFG", "LACR155LEIH"), Units = c("%", "Thous. of Persons", 
  "Thous. of Persons", "Thous. of Persons", "Thous. of Persons", 
  "Thous. of Persons"), Freq = c("M", "M", "M", "M", "M", "M"), 
      Seas = c("SA", "SA", "SA", "SA", "SA", "SA"), OriginalSource = c("U.S. Department of Labor: Bureau of Labor Statistics", 
      "Federal Reserve Bank of St. Louis", "Federal Reserve Bank of St. Louis", 
      "Federal Reserve Bank of St. Louis", "Federal Reserve Bank of St. Louis", 
      "Federal Reserve Bank of St. Louis"), Method = c("ImportXML", 
      "ImportXML", "ImportXML", "ImportXML", "ImportXML", "ImportXML"
      ), LinktoSource = c("", "", "", "", "", ""), Link.to.Data.Spreadsheet.Name = c("", 
      "", "", "", "", ""), Link.to.Data.Storage = c("", "", "", 
      "", "", ""), Link.to.Data.Manipulation.File = c(NA, NA, NA, 
      NA, NA, NA), Link.to.Data.Manipulation.File.1 = c(NA, NA, 
      NA, NA, NA, NA)), .Names = c("RegionalCoverage", "GeographicLevel", 
  "Category", "Sector", "Source2", "Title", "SeriesID", "Units", 
  "Freq", "Seas", "OriginalSource", "Method", "LinktoSource", "Link.to.Data.Spreadsheet.Name", 
  "Link.to.Data.Storage", "Link.to.Data.Manipulation.File", "Link.to.Data.Manipulation.File.1"
  ), row.names = c(27L, 34L, 44L, 46L, 47L, 48L), class = "data.frame")
  
  MakelineFred  &lt;- function(series, ylab="",xlab="", title="") {
  
  require(ggplot2)      # hadley's plotting framework
  require(scales)       # to adjust y axis scales
  require(ggthemes)     # extra themes including tufte
  require(xts)          # our favorite time series
  require(gridExtra)   # for adding a caption
  require(timeDate)    # for our prediction at the end
  require(quantmod)    # 
  
  # Get Data using quantmod
  data &lt;- getSymbols(series,src="FRED") #fred ignore from dates
  
  # convert the string df to object df
  data.xts &lt;- get(data)   
  
  ## convert data to data.frame
  df &lt;- data.frame(
  date=as.Date(index(data.xts)),
  value=as.numeric(data.xts))
  
  p &lt;- ggplot(df, aes(x=date, y=value)) 
  
  ## plot the line 
  p &lt;- p + geom_line()
  
  ## add plot title
  p &lt;- p + ggtitle(title)
  file &lt;- paste("_",series,".png",sep="")
  ggsave(file=file, plot=p,  width=6, height=4)
  </code></pre>
  
  <p>finally here is the <code>mapply</code> call.</p>
  
  <pre><code>mapply(MakelineFred, series=fred.M.SA$SeriesID, title=fred.M.SA$Title)
  </code></pre>