Write a variable and its metadata to cache
.write.cache(cache.hash, ...)No value is returned, this function is called for its side effects.
a data.frame with metadata about the variable, see details for more information.
extra parameters passed to save.
cache.hash is a data frame with two columns: variable and hash.
Row name VAR is the name of the variable to save.
Row name CODE is the hash value of the code to compute variable.
Row name DEPENDS.* are the dependent variables that CODE depends on.c
The helper function .create.cache.hash creates a suitable dataframe