expression evaluates to missing

[FAY FAY]

Dear Statalist:
Thank you very much, the problem has been solved.
I just have not figured out how to delete a previous post.
Sorry for the confusions.
regards

[Clyde Schechter]

Posts, once started, cannot be deleted. As you have seen, it is possible, for a time, to overwrite the original post and thereby eliminate its content. But we really request of Forum members that they not do this. There are Forum members, or even non-members, who read the Forum to learn Stata and statistics. I myself did this for many years, and it was a major contribution to my current level of knowledge. So even if you have solved your problem, it is helpful to others if you leave the original question there and, indeed, follow-up with a second post showing the solution you found! Statalist is not a help-line where you have a dialog with a technical support person. It is engagement in a community, and we ask that transactions be done in that spirit.

[Nick Cox]

Clyde is bang on here as usual. In fact, we explain this already in the FAQ Advice everyone is asked to read before posting. Emphasis added.

16. Should I close, delete, or edit threads I start?

Trying to wrap up a thread you started is helpful, especially if you report what solved your problem. You can then thank those who tried to help. Conversely, ignoring answers is less sociable, even if those answers did not solve your problem. "Thanks in advance" does not absolve you from either expectation.

Starting a thread does not convey ownership of that thread. Re-opening a thread by yourself or others is always allowed, and encouraged when any one has something relevant to add, say by reporting another solution, an update of a program, or a very similar question. Lapse of time is often not important: for example, it's fine to announce an update of a program in the same thread a few years after the original post. A new post always bumps a thread temporarily to the top of the list, so that additions can be noticed and read in context.

You cannot delete a thread you started. Please don't mangle your own posts starting a thread, even if you solved your problem yourself or realised that the question was silly. Explain the solution, even if it was trivial. Often someone else will have the same problem.

You can edit posts within a hour of posting. This allows fixes of many kinds, such as typo corrections, extra detail, or improved wording. Such edits within an hour include being able to delete any post that does not start a thread

[Bailey Stringer]

Hi Fay Fay, I am getting the same error as the one in the title of this post. Please could you post the solution that worked for you? Thanks!

[Nick Cox]

FAY FAY is long gone, it seems.