title: Combine Logical Operators
body: <p>I'm quite new to R and I have a simple question I just can't figure out a simple problem. 
  I want to combine two logical Statements  i.e. I want to exclude two Columns from my analysis
  To exclude only one value the code works fine and looks like this:</p>
  
  <p><code>df[ colnames(df) != "Total.Population", function(x){ x/df$Total.Population *1000 }</code></p>
  
  <p>So besides the population I also want to exclude the column Geocodes from my analysis. I tried a lot of diffrent stuff like</p>
  
  <p><code>df[ colnames(df) != "Total.Population"&amp;&amp;"Geocodes", function(x){ x/df$Total.Population *1000 }</code> </p>
  
  <p>but I just can't get it done to work for me...
  so any help would be great. Thx</p>