title: SQLDF Left Join in R
body: <p>My goal is to take 'matr', sort it by column c1, and keep unique(c1) where c2 = 1. For example, from this code...</p>
  
  <pre><code>c1 = c("a",'a','a','b','b','b','b','c','c')
  c2 = c(1,1,0,1,1,0,1,0,0)
  matr = as.data.frame(cbind(c1,c2))    
  one = sqldf('select distinct(c1),c2 from matr where c2 = 1')    
  vs = sqldf('select distinct(c1),c0,c2 from matr group by c1')
  sqldf('select matr.*,one.* from matr 
    left outer join one 
    where one.c1 = matr.c1')
  </code></pre>
  
  <p>arrive at:</p>
  
  <pre><code>c1 c2
  a  1
  b  1
  c  0
  </code></pre>
  
  <p>For some reason, i lose row c in the left join. I can only arrive at (through other joins) </p>
  
  <pre><code>c1 c2
  a  1
  b  1
  </code></pre>