title: Changing all values in a data frame with a data frame specifying replacement
body: <p>I have a question that seems simple, but I can't seem to find an answer to this problem. I am trying to replace all values generated in a williams design (values 1 - 4) with a character string TRT1, TRT2, etc.</p>
  
  <pre><code>d = data.frame(crossdes::williams(4))
  names(d) = c("Period 1", "Period 2","Period 3","Period 4")
  d2 = data.frame(treatmentNo = c(1,2,3,4), 
              treatmentName = c("TRT1","TRT2",
                                "TRT3", "TRT4"))
  </code></pre>
  
  <p>I would like to have everything in d changed from values to what is specified in d2. </p>
  
  <p>Thanks.</p>