[R] What will produce NA for lm()?

From: Guojun Zhu <shmilylemon_at_yahoo.com>
Date: Sun 07 May 2006 - 16:57:20 EST


I still works on the similar questions. I have a data frame, say d, with 33+1 colums (20 of them are 0/1 dummy variables) and about 1000 rows. Now I do the linear regression and get a NA for one of the dummy variables, say a. I check the data frame, using "d[d$a %in% 1,]" and found there are one row with no NA at all. And there are 800 0s in d$a. I know if there is no 1 in d$a or the no one full non-NA rwo with d$a==1, I will get NA for d$a. But I do not expect a NA in my case. What is other possibility to produce NA d$a? thanks.



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