title: Replacing values in DataFrame to NA in Julia
body: <p>What is the most elegant way to replace a value(say 99) to NA in a DataFrame in Julia?</p>
  
  <p>I am considering using an iterator to skim each row and check each value for 99, etc. I would like to know if there is a better way to do this.</p>
  
  <pre><code>using Taro
  Taro.init()
  tempdf =Taro.readxl("/path/to/xls/", "Sheet1", "A1:CW24983"; header=false)
  #Need one line command to replace all the 99s in the 24983 X 101 DataFrame to NA
  </code></pre>
  
  <p>Here is the MWE :</p>
  
  <pre><code>Pkg.add("RDatasets")
  using RDatasets, DataFrames
  datafr = dataset("datasets","anscombe")
  #Replace each instance of 10(for e.g : (1,X1), (1,X2)) with NA
  </code></pre>
  
  <p>Edit 1 : Question for Julia similar to one <a href="https://stackoverflow.com/questions/12835942/fast-replacing-values-in-dataframe-in-r">here</a> for R.</p>