.Hello everyone, I am learning the MLE model and practicing through the book examples using Stata12. Even applying the given example of the book is continuously showing this error. Please suggest me the reason of this error. I am stuck with this problem and unable to proceed. ml check description is also mentioned below for clarificaton
program myprobit_lf
1. version 11
2. args lnfj xb
3. quietly replace ‘lnfj’ = ln(normal( ‘xb’)) if $ML_y1 == 1
4. quietly replace ‘lnfj’ = ln(normal(-‘xb’)) if $ML_y1 == 0
5. end
ml check

Test 1: Calling myprobit_lf to check if it computes log likelihood and
does not alter coefficient vector...
FAILED; myprobit_lf returned error 198.

Here is a trace of its execution:
------------------------------------------------------------------------------
-> myprobit_lf __000008 __000009
- `begin'
= capture noisily version 12: myprobit_lf __000008 __000009
---------------------------------------------------------------------------------------------------------- begin myprobit_lf ---
- version 11
- args lnfj xb
- quietly replace ‘lnfj’ = ln(normal( ‘xb’)) if $ML_y1 == 1
= quietly replace ‘lnfj’ = ln(normal( ‘xb’)) if died == 1
‘lnfj’ invalid name
------------------------------------------------------------------------------------------------------------ end myprobit_lf ---
- `end'
= set trace off
------------------------------------------------------------------------------
Fix myprobit_lf.
r(198);

.