title: Get ggplot2 legend to display percentage sign in r
body: <p>Below is a reproducible example of the issue I am trying to solve. I have created a heatmap of sorts in ggplot2 and things have been going well. Since I have put percentage signs on the data to use with geom_text I would like to make the legend of geom_tile also to display percent signs (I can only multiply the actual values by 100 right now). Ideally I would like the legend bar on the right to show 8%, 4%, 0%, -4%, -8%.</p>
  
  <pre><code>#load in libraries
  require(plyr)
  require(dplyr)
  require(reshape2)
  require(ggplot2)
  require(scales)
  
  testDF &lt;- structure(list(strategies = structure(c(8L, 7L, 6L, 5L, 4L, 3L, 
                                                    2L, 1L), .Label = c("Class 1", "Class 2", 
                                                                        "Class 3", "Class 4", "Class 5", "Class 6", 
                                                                        "Class 7", "Class 8"), class = "factor"), 
                           School1 = c(0.0355662887589396, 0.0316753241146625, 0.00606392341292672, 
                                       0.0250738342627283, -0.0405709181701368, 0.0237665074609996, 
                                       0.00587364885411765, -0.0343914002059331), School2 = c(NA, NA, 
                                                                                              NA, 0.0225535750673764, NA, -0.00448947685878404, NA, -0.0446386763157662
                                       ), School3 = c(NA, NA, NA, 0.0261099462365593, NA, 0.0199735626692146, 
                                                      NA, -0.0272279264519992), School4 = c(NA, NA, NA, 0.0164004151291513, 
                                                                                            NA, 0.00567638888888868, NA, -0.0384017249374949)), .Names = c("schools", 
                                                                                                                                                           "School1", "School2", "School3", "School4"), row.names = c(NA, -8L), class = "data.frame")
  
  
  GraphMelt &lt;- melt(testDF)
  GraphMelt &lt;- GraphMelt %&gt;% mutate(text = sprintf("%1.2f%%", 100*value))
  GraphMelt[,"text"] &lt;- ifelse(GraphMelt[,"text"]=="NA%",NA,GraphMelt[,"text"])                                    
  p &lt;- ggplot(GraphMelt, aes(variable, schools))
  p &lt;- p + geom_tile(aes(fill = value*100), colour =   "white") + geom_text(aes(label=text),size=7)
  p &lt;- p + scale_fill_gradient(low = "red", high = "green",limits=c(-8,8))
  p &lt;- p + theme(
    axis.text.x= element_text(color="black", size=14, vjust=0.5),
    axis.text.y= element_text(color="black", size=14, vjust=0.5),
    axis.title.y = element_text(color="black",size=14, vjust=0.5),
    plot.title = element_text(color="black",size=14,face="bold", hjust=0.5,vjust=1),
    panel.background = element_blank(),
    legend.position="right",
    legend.title = element_blank(),
    legend.key = element_rect(fill="white"), legend.background = element_rect(fill=NA)
  )
  p &lt;- p + xlab("") + ylab("") + ggtitle("Schools")
  </code></pre>