.. _ExpressionParameter:


Expression parameter
--------------------


The parameter is described by a general mathematical expression depending on the names of the input parameters (either from the design space and environment or from the input of the  transformation that the parameter belongs to.

.. _ActiveLearning.trans.expression.name:


name (str)
""""""""""
   The name of the parameter. 

   Default: This value has no default and must be provided

.. _ActiveLearning.trans.expression.expression:


expression (str)
""""""""""""""""
   String defining a mathematical expression of other parameters. The expression can contain numbers as either integers or floating-point reals in standard or exponential notation (``0.0012`` or ``1.2E-3``) as well as the constants ``E`` (Euler constant) and ``PI`` (:math:`\pi`). Parameter names may not start with the capital letters "``E``" nor "``PI``". Supported operations are ``+``, ``-``, ``*``, ``/``, ``^``, supported single-argument functions are ``sqrt``, ``sinh``, ``sin``, ``asinh``, ``asin``, ``cosh``, ``cos``, ``acosh``, ``acos``, ``tanh``, ``tan``, ``atanh``, ``atan``, ``exp``, ``log10``, ``log``, ``erfinv``, ``erf``, ``abs``, ``trunc``, ``round``, ``sign``, and supported multi-argument functions are ``max``, ``min``. 

   Default: This value has no default and must be provided

   .. admonition:: Example

      Expression depending on ``param1`` and ``param2``.

      .. code-block:: python

         '1.0 - param1/param2'


.. _ActiveLearning.trans.expression.bounds:


bounds (list[float])
""""""""""""""""""""
   The lower and upper bound of possible parameter values. This is required to define a domain of possible length scales for this parameter. Hence, only a rough estimate is often sufficient for complex expression. 

   Default: This value has no default and must be provided