When an endogenous is declared with “var(log)”, say “y”:
– creates an auxiliary named “LOG_y”
– replaces “y(±l)” everywhere by “exp(LOG_y(±l))”
– adds a new auxiliary equation “y=exp(LOG_y)”
– adds a new definition “LOG_y=log(y)” in set_auxiliary_variables.m and
dynamic_set_auxiliary_series.m files
This option also works in conjunction with “deflator=…”, such as “var(log,
deflator=…)” (the “log” must appear befor “deflator”). There are no provisions
for combining “log” with “log_deflator”, because that would not make much sense
from an economic point of view (amounts to taking the log two times).
Ref. dynare#349
This is a more natural semantics.
Incidentally, this fixes a bug in the variable mapping (M_.mapping) where some
endogenous, appearing in a log() in a VAR or TCM, would not be mentioned (e.g.
in the var-expectations/7/example1.mod test, and many others).
By the way:
– Fix and improve the explanation of the purpose of the orig_symb_id and
orig_lead_lag fields for auxvars
– Factorize the code that prints those fields in MATLAB and JSON output
The logic was flawed in several ways. In particular, the test files
pac/trend-component-{3,10,11}/example1.mod would return A0 and A0star matrices
where the (2,2) element was incorrectly zero.
The case of a diff aux var corresponding to a complex expression was not
correctly handled, and could lead to a value -1 being returned by these
methods.
This field contains a string representation of the expression that the
auxiliary variable replaces.
It is non-empty for all auxiliary variables, except for Lagrange multipliers.
Ref. dynare#773
We can therefore manipulate objects by value rather than by pointers, which
saves a lot of memory manipulations (and avoid potential segfaults and memory
leaks).
Note that there is no default action ("$$ = $1") when using the variant type,
so we add them explicitly.
In the absence of this option, if a var_model statement(s) is present, then aux vars/eqs are created for the same types of unary operators but only for equations specified in the var_model statement
In the absence of both this option and var_model statements, no unary op auxiliary variables are created
diffs continue to be substituted everywhere; for the moment auxiliary variables are created for diffs of expressions. A forthcoming change will allow auxiliary variables created for diffs of expressions to be linked with their lagged expressions as is currently the case for diffs of variables