title: r knitr chunk options for figure height / width are not working
body: <p>I used to use <code>knitr</code> in <code>R</code> to produce reports from the <code>.Rnw</code> format. In my reports I often put a plenty of plots and manipulated their size with the use of chunk optios, e.g.: </p>
  
  <pre><code>\begin{figure}[h!]
  \centering
  &lt;&lt;fig.width=6, fig.height=4, out.width='.89\\linewidth'&gt;&gt;=
  
  plot(mtcars)
  
  @
  \caption{}
  \end{figure}
  </code></pre>
  
  <p>It was few months ago. Then I moved to another environment, reinstalled R and these options seem no longer work - <strong>the plot size stays unchanged on the PDF output</strong>! </p>
  
  <p>Here comes all the lines of code regarding any option settings. I am looking forward any suggestions what am I doing wrong. </p>
  
  <pre><code>&lt;&lt; &gt;&gt;=
  library(knitr)
  knitr::opts_chunk$set(echo=F, eval=T, message = F, warning=F, cache = F, fig=TRUE)
  @
  
  \begin{figure}[h!]
  \centering
  &lt;&lt;fig.width=10, fig.height=3, out.width='.89\\linewidth', fig=TRUE, echo=F&gt;&gt;=
  plot(mtcars)
  @
  \caption{mtcars plot}
  \end{figure}
  </code></pre>
  
  <p>Exactly the same result appears when I use <code>&lt;&lt;fig.width=10, fig.height=3, fig=TRUE, echo=F&gt;&gt;=</code>. </p>
  
  <p><strong>Session info</strong></p>
  
  <pre><code>&gt; sessionInfo()
  R version 3.1.1 (2014-07-10)
  Platform: x86_64-pc-linux-gnu (64-bit)
  
  locale:
   [1] LC_CTYPE=en_US.UTF-8      
   [2] LC_NUMERIC=C              
   [3] LC_TIME=pl_PL.UTF-8       
   [4] LC_COLLATE=en_US.UTF-8    
   [5] LC_MONETARY=pl_PL.UTF-8   
   [6] LC_MESSAGES=en_US.UTF-8   
   [7] LC_PAPER=pl_PL.UTF-8      
   [8] LC_NAME=C                 
   [9] LC_ADDRESS=C              
  [10] LC_TELEPHONE=C            
  [11] LC_MEASUREMENT=pl_PL.UTF-8
  [12] LC_IDENTIFICATION=C       
  
  attached base packages:
  [1] splines   stats4    stats     graphics  grDevices
  [6] utils     datasets  methods   base     
  
  other attached packages:
   [1] bootstrap_2014.4     dplyr_0.3.0.9000    
   [3] het.test_0.1         vars_1.5-2          
   [5] lmtest_0.9-33        urca_1.2-8          
   [7] strucchange_1.5-0    sandwich_2.3-2      
   [9] zoo_1.7-11           MASS_7.3-34         
  [11] VGAM_0.9-6           ggplot2_1.0.0       
  [13] manipulate_0.98.1078
  
  loaded via a namespace (and not attached):
   [1] assertthat_0.1   colorspace_1.2-4 DBI_0.3.1       
   [4] digest_0.6.4     evaluate_0.5.5   formatR_1.0     
   [7] grid_3.1.1       gtable_0.1.2     htmltools_0.2.6 
  [10] knitr_1.7        labeling_0.3     lattice_0.20-29 
  [13] lazyeval_0.1.9   magrittr_1.0.1   munsell_0.4.2   
  [16] parallel_3.1.1   plyr_1.8.1       proto_0.3-10    
  [19] Rcpp_0.11.3      reshape2_1.4     rmarkdown_0.3.9 
  [22] scales_0.2.4     stringr_0.6.2    tools_3.1.1     
  [25] yaml_2.1.13    
  </code></pre>
  
  <p><strong>PDF outpout screenshot</strong> (unchanged size)</p>
  
  <p><img src="https://i.stack.imgur.com/l3nAG.png" alt="enter image description here"></p>