.. _D4.02.02:

**d4.02.02** sd_function data structures
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**Summary:**

The types of sd_function concepts represent functions (in the mathematical sense of the term) of one or two variables.

Functions have real values, function_C have complex values. In the rest of this document, we will only talk about functions with real values (function), knowing that everything can be transposed to function_C.

A function is by nature "tabulated": that is to say that it is only known at certain points. In this case, its evaluation may require interpolation or extrapolation.

A formula is "interpreted": its representation (data structure) then contains the mathematical expression of the function.

**Note**:

*A formula can be tabulated (for certain values of its variable) by the command* *CALC_FONC_INTERP. For a tabulated function, the evaluation at a point different from the tabulation points can be done by interpolation or extrapolation. A formula can have as many variables as needed. In contrast, tabulated functions can only have* :math:`\mathrm{0,}1` *or* :math:`2` *variables. We will then speak of "constant function", "function" or "sheet". The variables of a function (like its result) are "typed": 'TEMP', 'INST', 'EPSI',... We will then talk about the name of the parameters and the result.*

**Table of Contents**




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    self

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    Structure_de_donn_es
    Contenu_des_objets_de_base
    Exemples