title: import specific rows from "txt" into R
body: <p>I have a "example.txt" document just as follows:</p>
  
  <pre><code>SIGNAL: 40 41 42                                            
  0.406   0.043   0.051   0.021   0.013                   
  0.056   0.201   0.026   0.009   0.000                   
  0.000   0.128   0       0.009   0.000                               
  TOTAL: 0.657                                            
  SIGNAL: 44 45 46 48                                         
  0.128   0.338   0.026                       
  0.333   0.03    0.000                           
  0.060   0.013   0.004                           
  0.009   0.017   0.009                           
  0.013   0       0.000                           
  TOTAL: 0.704                                            
  SIGNAL: 51 52 54                                            
  0.368   0.081   0.085   0.004                       
  0.162   0.09    0.064   0.073                       
  0.013   0.017   0.009   0.000                       
  TOTAL: 0.266                                            
  SIGNAL: 60 61 62 63 64 65 66 67                                         
  0.530   0.030                                   
  0.009   0.179                                   
  0.154   0.004                                   
  0.068   0.009                                   
  TOTAL: 0.796    
  </code></pre>
  
  <p>I want to import the rows between "SIGNAL: 44 45 46 48" and "TOTAL: 0.704" into R, I use <code>read.table("example.txt",skip=6 ,nrow=5)</code> to extract these specific rows, it works.</p>
  
  <pre><code>     V1    V2    V3
  1 0.128 0.338 0.026
  2 0.333 0.030 0.000
  3 0.060 0.013 0.004
  4 0.009 0.017 0.009
  5 0.013 0.000 0.000
  </code></pre>
  
  <p>However, my real data (has 450,000 rows) is very big, if I want to extract the rows between "SIGNAL: 3000 3001 3002 3003" and the next"TOTAL", how can I do with it? Thank you so much!</p>