How to set all missing values to zero for all variables?

[ChrisGermain]

Thank you very much! One other question:

1) How can I replace a missing value for a different variable using the mean of a group?

I have missing values for a variable "area" and I want to replace the missing values with the mean of "area" by "neighborhood", where values are not missing.

[PeterClemmensen]

Use PROC STDIZE as in the replace with zero case and use the MISSING=MEAN instead and the BY Statement to specify your By-Group