r - How to use lm.fit instead on lm -

i want use lm.fit speed, second version gives nas

 sum <-   summary(lm(y~x))  slope <-  sum$coefficients[2] 

or

 sum <-   lm.fit(as.matrix(x,ncol=1),y)  slope <-  sum$coefficients[2] 

edit 1

i see sum$coefficients has 1 value. why , it? doesn't explain this

it easier reproducible example.

however, guess missing intercept in second case. try lm.fit(cbind(1,x),y) , see if gives comparison looking for.

other differences due other preprocessing lm before calling lm.fit, don't know without seeing x. things removing missing values, expanding factor dummy variables result in differences.