title: How to create an empty R vector to add new items
body: <p>I want to use R in Python, as provided by the module Rpy2. I notice that R has very convenient <code>[]</code> operations by which you can extract the specific columns or lines. How could I achieve such a function by Python scripts?</p>
  
  <p>My idea is to create an R vector and add those wanted elements into this vector so that the final vector is the same as that in R. I created a <code>seq()</code>, but it seems that it has an initial digit 1, so the final result would always start with the digit 1, which is not what I want. So, is there a better way to do this?</p>