title: Plotting multiple histograms in same panel
body: <p>I am trying to plot multiple histograms of some variables in a data frame in the same panel. Here is some following code:</p>
  
  <pre><code> library(lattice) 
   dd &lt;- data.frame(gp = factor(rep(paste('Group', 1:6, sep = ''), each = 
   100)), x = rnorm(600)) 
   histogram( ~ x | gp, data = dd) 
   histogram( ~ x | gp, data = dd, as.table = TRUE) 
  </code></pre>
  
  <p>This is putting the data x into the groups 1 to 6. In a given dataframe, we already have the numbers in particular categories. For example, suppose I want to plot a histogram of height, weight and average blood pressure (variables in a date frame) in the same panel. How would I do this without having to form a new data set and groups 1 to 3?</p>