title: select a part of string in R
body: <p>i have a column of strings that looks like this : </p>
  
  <pre><code> Topology=o5-22i34-56o74-96i117-139o159-181i210-232o247-269i
   Topology=o4-26i35-57o77-99i119-138o161-183i216-238o248-270i
   Topology=o4-21i32-54o69-91i112-134o156-178i215-237o252-271i
   Topology=i20-42o65-84i105-127o158-180i212-234o249-271i     
   Topology=o5-27i39-61o76-98i118-140o151-173i194-213o 
  </code></pre>
  
  <p>I want to get the first number after equal sign and the last number in the string. the output should be something like</p>
  
  <pre><code>    5,269
      4,270
      4,271
      20,271
      5,213
  </code></pre>