title: How do I suppress this output?
body: <p>I have a code chunk in an R Markdown file.</p>
  
  <pre><code>```{r}
  library(UsingR)
  ```
  </code></pre>
  
  <p>Using knitHTML to compile causes the following output, which never happened before I updated to the latest versions of R and RStudio:</p>
  
  <pre><code>## Loading required package: MASS
  ## Loading required package: HistData
  ## Loading required package: Hmisc
  ## Loading required package: grid
  ## Loading required package: lattice
  ## Loading required package: survival
  ## Loading required package: splines
  ## Loading required package: Formula
  ## 
  ## Attaching package: 'Hmisc'
  ## 
  ## The following objects are masked from 'package:base':
  ## 
  ##     format.pval, round.POSIXt, trunc.POSIXt, units
  ## 
  ## Loading required package: aplpack
  ## Loading required package: tcltk
  ## Loading required package: quantreg
  ## Loading required package: SparseM
  ## 
  ## Attaching package: 'SparseM'
  ## 
  ## The following object is masked from 'package:base':
  ## 
  ##     backsolve
  ## 
  ## 
  ## Attaching package: 'quantreg'
  ## 
  ## The following object is masked from 'package:Hmisc':
  ## 
  ##     latex
  ## 
  ## The following object is masked from 'package:survival':
  ## 
  ##     untangle.specials
  ## 
  ## 
  ## Attaching package: 'UsingR'
  ## 
  ## The following object is masked from 'package:survival':
  ## 
  ##     cancer
  </code></pre>
  
  <p>How can I suppress this output? Note: echo=FALSE did not work.</p>