title: R format number syntax
body: <p>I'm trying to display some numbers as percentages.</p>
  
  <pre><code>data &lt;- read.csv(
  "http://archive.ics.uci.edu/ml/machine-learning-databases/adult/adult.data", 
      header = FALSE, 
      na.strings = "?", 
  strip.white = TRUE
  )
  colnames(data) &lt;- c("age", "workclass", "fnlwgt", "education", "education-num", "marital-status", "occupation", "relationship", "race", "sex", "capital-gain", "capital-loss", "hours-per-week", "native-country", "prediction")
  
  colSums(is.na(data))/nrow(data)*100
  </code></pre>
  
  <p>The last command there outputs</p>
  
  <pre><code>       age      workclass         fnlwgt      education  education-num marital-status     occupation   relationship 
    0.000000       5.638647       0.000000       0.000000       0.000000       0.000000       5.660146       0.000000 
        race            sex   capital-gain   capital-loss hours-per-week native-country     prediction 
    0.000000       0.000000       0.000000       0.000000       0.000000       1.790486       0.000000 
  </code></pre>
  
  <p>It seems like it would be hard to format those, but honestly I'm still thinking R works via black magic so is there some black magic that can format those the same way <code>sprintf("%.1f %%", 100*somePercentage)</code> formats <code>somePercentage</code>?</p>
  
  <p>Hoped for output:</p>
  
  <pre><code>age      workclass         fnlwgt      education
    0.0%       5.63%         0.0%          0.0%      
  </code></pre>