I'm running a regression model with dummy variables and getting NA 
for some coefficients. I believe this due to singularity problem. How can I exclude some of the dummy variables from the regression model in R to take care of this issue. I read in R help that lm() method takes care of this issue automatically. But in my case its not happening? Any pointers would be of great help.
   
  Regression Model: 
   
  reg06 <- lm(mydf$y~ mydf$x1 + factor(mydf$x2) + factor(mydf$x3)+ factor(mydf$x4) +  mydf$x5, singular.ok = TRUE)
   
  Thanx in advance
   
  Sachin

		
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