title: Using R to select data based on another dataset
body: <p>I have a large datasets (d1)like this below:</p>
  
  <pre><code>SNP Position    Chromosome
  rs1 10010   1
  rs2 10020   1
  rs3 10030   1
  rs4 10040   1
  rs5 10010   2
  rs6 10020   2
  rs7 10030   2
  rs8 10040   2
  rs9 10010   3
  rs10 10020  3
  rs11 10030  3
  rs12 10040  3
  </code></pre>
  
  <p>I also have a dataset(d2) like below:</p>
  
  <pre><code>SNP Position    Chromosome
  rsA 10015   1    
  rsB 10035   3
  </code></pre>
  
  <p>Now, i want to select a range of SNPs in d1 based on the d2(Position+-5 and the same chromosome), and write the results to txt file, the results should be like this:</p>
  
  <pre><code>SNP(d2) SNP(d1) Position(d1)    Chromosome
  rsA rs2 10020   1
  rsA rs3 10030   1
  rsB rs11    10030   3
  rsB rs12    10040   3 
  </code></pre>
  
  <p>I am new in R, can anyone please tell me how to do that in R? You kind of reply are highly appreciated.</p>