====== Equation Module ======

//Equation//, as the name implies, are to be used where calculations are to be performed on a number of input variables in order to obtain the value of an output one.

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===== Endpoint =====
The //Equation// endpoint provides a RESTful interface to interact with //Equation// objects in the database. It allows authenticated users to create, update, and delete their own //Equations// objects.

The base URL for the //Equation// endpoint is [[https://datamanagerapi.solver-ai.com/api/data/equations/]].

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===== HTTP Methods =====
  * **GET** //equations//: Retrieves a list of all Equation objects associated with the authenticated user.
  * **POST** //equations//: Creates a new Equation object associated with the authenticated user.
  * **GET** //equations/{id}//: Retrieves the Equation object with the specified //id//.
  * **PUT** //equations/{id}//: Updates the Equation object with the specified //id//.
  * **PATCH** //equations/{id}//: Updates part of an Equation object with the specified //id//.
  * **DELETE** //equations/{id}//: Deletes the Equation object with the specified //id//.

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===== Data =====
An //Equation// can be set up via the [[https://www.solver-ai.com/api|Browsable API]] (2 - Module Management) or programmatically  (more on this [[:api_clients|here]]).

The parameters required for creating an Equation module are:

  * **Name**: Unique name identifying the Equation.
  * **EquationString**: Is the equation.
  * **VariablesString**: Is the list of the input variables (the output variable is deducted from the //EquationString//).
  * **VectorizationIndices (optional)**: Indices used for vectorizing the equation.

Following is an example of the data when setup through the Browsable API:

<code>
Name: Example Equation
EquationString: z = x + y
VariablesString: x, y
VectorizationIndices: 3-5
</code>

**More on VectorizationIndices**

The //VectorizationIndices// can be left:

  * empty
  * be specified as a range (e.g., 3-5)
  * or be specified as a list of comma separated indices (e.g., 7, 8, 10)

For the example above, //VariablesString// represents the inputs to the equation, which are 'x' and 'y'. The //VectorizationIndices// field is set to '3-5', indicating that this equation should be vectorized over the indices 3, 4, and 5. This is equivalent to defining three separate equations:

  * z_3 = x_3 + y_3
  * z_4 = x_4 + y_4
  * z_5 = x_5 + y_5'

If //VectorizationIndices// is left empty, then the code will not be vectorized and the naming of the variables will remain as defined by the //VariablesStringIn// and //VariablesStringOut//.

**More on the EquationString**

The //EquationString// is python 3.9 compatible. Together with the equation string most **numpy** operations are supported, except those involving file operations. **numpy** can be used within the equation as for example:

;#;
z = x + np.cos(y)
;#;

The supported functions are:
  * np.abs
  * np.sqrt
  * np.log
  * np.log2
  * np.log10
  * np.exp
  * np.sin
  * np.cos
  * np.tan
  * np.arcsin
  * np.arccos
  * np.arctan
  * np.sinh
  * np.cosh
  * np.tanh
  * np.arcsinh
  * np.arccosh
  * np.arctanh
  * np.ceil
  * np.floor
  * np.round

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===== Permissions =====
Only authenticated users can interact with this endpoint, this can be done via the [[https://www.solver-ai.com/api|API]] page or pragrammatically via a token, which can be obtained from the [[https://www.solver-ai.com/accountmanagement|Account]] page.

All //Equation// created will be associated with the authenticated user, and and will not be accessible by other users.

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===== Notes =====
  * If you attempt to delete an //Equation// that is used in a problem, the request will be denied with a 403 Forbidden status code.
  * For information on doing the same programmatically follow the documentation relative to the [[:api_clients|API Clients]].