title: Adding custom legend to fourfold()
body: <p>Does anyone know how to add custom legends to fourfold() from the vcd package? </p>
  
  <p>I can add to fourfoldplot() in base using the legend() function, but I want to use the custom colours for OR≈1.0 and OR≠1.0 that comes with fourfold()</p>
  
  <p>When I create a plot using fourfold() and then try to add a legend using legend() I get the following error...</p>
  
  <p>Error in strwidth(legend, units = "user", cex = cex, font = text.font) :</p>
  
  <p>plot.new has not been called yet</p>
  
  <p>Here is an example:</p>
  
  <pre><code># install.packages("vcd")
  library(vcd)
  
  x&lt;-matrix(c(1146,210,471,897,
              669,687,809,559,
              761,595, 1030,338,
              1227,129,1306,62,
              844,737,773,370,
              1134,447,344,799,
              1001,580,790,353,
              1461,120,1072,71,
              820,837,797,270,
              866,791,612,455, 
              1370,287,421,646, 
              1583,74,950,117, 
              1462,1056,155,51, 
              1349,1169,129,77,
              1688,830,103,103, 
              2419,99,114,92),ncol=8,nrow=8)
  x
  x&lt;-as.table(x)
  x&lt;-as.data.frame(x)
  
  xarray&lt;-array(x$Freq, dim=c(2,2,16))
  xarray&lt;-aperm(xarray,c(2,1,3))
  dimnames(xarray)[[1]] &lt;- c("No", "Yes")
  dimnames(xarray)[[2]] &lt;- c("No", "Yes")
  dimnames(xarray)[[3]] &lt;- c("Morning:Morning","Morning:Afternoon","Morning:Evening","Morning:Night-time",
                                   "Afternoon:Morning","Afternoon:Afternoon","Afternoon:Evening","Afternoon:Night-time",
                                   "Evening:Morning","Evening:Afternoon","Evening:Evening","Evening:Night-time",
                                   "Night-time:Morning","Night-time:Afternoon","Night-time:Afternoon","Night-time:Night-time")
  names(dimnames(xarray)) &lt;- c("Post", "Pre", "Time of day")
  
  fourfold(xarray, c("#99CCFF", "#6699CC", "#999999", "#E69F00", "#56B4E9", "#009E73"), ticks = 0.25,
           main = "Did you usually train in the morning, afternoon, evening or night-time?", p_adjust_method="bon") 
  
  legend("right",legend = c("Non Sig.","Sig"), fill = c("#E69F00", "#009E73"))
  </code></pre>