st: What does Wald=. or F=. mean?

["Nirina F" <fstata@gmail.com>]

Good day,

I run linear probability model  which is just
reg y=ax+b  where y is taking value 0, 1 and I get the following:

Linear regression                                      Number of obs =      49
                                                       F( 29,    18) =       .
                                                       Prob > F      =       .
                                                       R-squared     =  0.8884
                                                       Root MSE      =  .27512


Now I run -probit-,

I get the following:
Probit regression                                 Number of obs   =         23
                                                  Wald chi2(13)   =          .
                                                  Prob > chi2     =          .
Log pseudolikelihood = -2.826e-08                 Pseudo R2       =     1.0000

I know I am getting wierd coefficient and some coef report zero
standard errors.
Something is wrong but not sure how to explain this ". " for Wald and F stat.
Thank you in advance,
Nirina
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