Axis Calibration and Dependency
===============================

Axis Calibration
----------------

In some cases, motor axis values require calibration.
The ``PreCorrection`` utility enables axis calibration using user-defined correction functions or data.

Suppose the motor axis "x" requires calibration, and the relationship between the raw position and the corrected position is given by a set of data points.
These data can be stored in a NumPy ``.npz`` file with the following structure:








Axis Dependency
---------------

``PreCorrection`` also supports defining dependencies among axes.
Suppose the position of "y" must always follow a fixed function of "x", for example, ``y = x/2`` while only "x" is directly controlled.

A simple GUI combining a motor and a corrector can be constructed as follows:

.. code-block:: python

    from lys.widgets import LysSubWindow
    from lys.Qt import QtWidgets
    from lys_instr import PreCorrector, gui, dummy
    from lys_instr.PreCorrection import _FunctionCombination, _InterpolatedFunction

    class Window(LysSubWindow):
        def __init__(self, parent=None):
            super().__init__(parent)
            self._motor = dummy.MultiMotorDummy("x", "y")
            self._corrector = PreCorrector([self._motor])
            self._initLayout()
            self.adjustSize()

        def _initLayout(self):
            _motorGUI = gui.MultiMotorGUI(self._motor, axisNamesSettable=("x",), axisNamesJoggable=("x",)) # only enable "x" axis control
            _correctorGUI = gui.PreCorrectorGUI(self._corrector)

            self._tab = QtWidgets.QTabWidget()
            self._tab.addTab(_motorGUI, "Motor")
            self._tab.addTab(_correctorGUI, "PreCorr")

            VBox = QtWidgets.QVBoxLayout()
            VBox.addWidget(self._tab)

            HBox = QtWidgets.QHBoxLayout()
            HBox.addLayout(VBox)

            w = QtWidgets.QWidget()
            w.setLayout(HBox)
            self.setWidget(w)


The resulting GUI appears as follows. Only the "x" axis is enabled for control:

.. image:: /lys_instr_/tutorial_/preCorrection_1.png

.. image:: /lys_instr_/tutorial_/preCorrection_2.png

In the **PreCorr** tab, right-click on the tree space and select "Add Target" to add a target axis, i.e., "y".
Then, right-click on the target "y" and select "Add Variable", choosing "x" as the dependency axis.
Next, double-click on the expression space of target "y" to enter ``x/2``.

.. image:: /lys_instr_/tutorial_/preCorrection_3.png

Now, when you enter a target position for "x" in the **Motor** tab and click **Go**, the motor will move "x" to the specified position and "y" will automatically be set to half of "x".

.. image:: /lys_instr_/tutorial_/preCorrection_4.png