Numeric::Interpolator::Linear
=============================

:bdg-link-secondary-line:`src/Numeric/Interpolator/Linear.H <../../../doxygen/Numeric_2Interpolator_2Linear_8H_source.html>`

This is a general-purpose routine for specifying time-interpolated
quantities in an input file.
Interpolators obey the following syntax:

.. code-block:: bash

   (t1,t2,..,tn;v1,v2,...,vn)

where :code:`tn` are times and :code:`vn` are values at those times.

:bdg-danger-line:`Note: do not include whitespace in an interpolator, this will mess with the parser.`

Interpolators can usually be used in place of regular numbers, but only
when supported by the calling parse function.

For instance, the `BC::Operator::Elastic::TensionTest` allows the user to specify
fixed displacement; for instance, to specify a value of 0.1:

.. code-block:: bash

   bc.tenstion_test.disp = 0.1

However, it may be desirable to change the value over time.
In this case, one may specify an interpolator string instead:

.. code-block:: bash

   bc.tenstion_test.disp = (1.0,1.5,2.0;0.0,0.1,0.0)

This will cause the displacement value to be zero for :code:`t<1.0`; 
ramp to :code:`0.1` as :code:`1.0<t<2.0`; 
ramp back to :code:`0.0` as :code:`2.0<t<3.0`; 
and then remain at the constant value of :code:`3.0` for :code:`t>3.0`.

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