Defines a numeric independent variable. The list of valid attributes comprises the name of the variable,
the exponent to be used, and the coefficient by which the values of this variable must be multiplied.
Note that the exponent defaults to 1, hence it is not always necessary to specify. Also, if the input value
is missing, the result evaluates to a missing value.
Defines a numeric independent variable. The list of valid attributes comprises the name of the variable, the exponent to be used, and the coefficient by which the values of this variable must be multiplied. Note that the exponent defaults to 1, hence it is not always necessary to specify. Also, if the input value is missing, the result evaluates to a missing value.