Dear R users,
I am running a linear regression in R. My observations are Census Tracts in
several metropolitan areas (MSAs). In my data set, each MSA has at least 50
observations. I use factor(msa_code) in the lm formula to control for
metropolitan fixed effects. But I kept getting something like this:
.....
factor(msa_code)12420 4.910e-01 1.517e-01 3.237 0.001221 **
factor(msa_code)12580 1.966e-01 6.861e-02 2.865 0.004194 **
factor(msa_code)14460 -3.892e-02 1.653e-02 -2.355 0.018601 *
factor(msa_code)16980 -2.873e-01 3.278e-02 -8.764 < 2e-16 ***
factor(msa_code)17140 1.088e-01 6.771e-02 1.607 0.108127
factor(msa_code)17460 -1.173e-01 4.380e-02 -2.678 0.007441 **
factor(msa_code)19100 1.368e-01 5.550e-02 2.465 0.013753 *
factor(msa_code)19740 5.819e-01 1.173e-01 4.962 7.33e-07 ***
factor(msa_code)19820 -4.214e-01 6.641e-02 -6.346 2.51e-10 ***
factor(msa_code)26420 1.258e-01 7.541e-02 1.668 0.095486 .
factor(msa_code)28140 2.010e-01 3.847e-02 5.224 1.85e-07 ***
factor(msa_code)29820 7.102e-02 6.593e-02 1.077 0.281435
factor(msa_code)31100 -4.832e-01 1.088e-01 -4.440 9.28e-06 ***
factor(msa_code)33100 -2.534e-01 6.391e-02 -3.965 7.49e-05 ***
factor(msa_code)33460 5.229e-02 7.891e-02 0.663 0.507609
factor(msa_code)35620 -3.197e-01 7.565e-02 -4.225 2.45e-05 ***
factor(msa_code)36740 1.269e-01 6.948e-02 1.826 0.067868 .
factor(msa_code)37980 1.394e-01 4.388e-02 3.178 0.001497 **
factor(msa_code)38060 -6.935e-02 6.124e-02 -1.132 0.257540
factor(msa_code)38300 1.647e-01 3.986e-02 4.133 3.67e-05 ***
factor(msa_code)38900 2.605e-01 1.420e-01 1.835 0.066664 .
factor(msa_code)39300 -9.612e-02 4.704e-02 -2.043 0.041103 *
factor(msa_code)40140 -2.353e-01 3.562e-02 -6.605 4.59e-11 ***
factor(msa_code)40900 NA NA NA NA
factor(msa_code)41740 NA NA NA NA
factor(msa_code)41860 NA NA NA NA
factor(msa_code)42660 NA NA NA NA
factor(msa_code)45300 NA NA NA NA
factor(msa_code)47900 NA NA NA NA
I wonder why I kep getting those "NAs". Thank you!
Gary
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