.. highlightlang:: us

.. index:: upfirdn

.. _upfirdn:

upfirdn
=======

.. us.tag upfirdn NOTREADYENGLISH fft New5503

:ref:`upfirdn` is a polyphase FIR resampling function.

.. function:: y = upfirdn(x, h, p, q);

.. us.return

**Return Value**

*y* is erf(x).

.. us.params

**Parameters**

.. uparam:: x

   *x* is the input signal.

.. uparam:: h

   *h* is a FIR impulse response sequence vector.

.. uparam:: p

   *p* upsampling factor.

.. uparam:: q

   *q* downsampling factor.

.. us.comment

**Comment**

The length of the output, y, is ``ceil(((len(x)-1)*p+len(h))/q);``

* upsampling (that is, zero-insertion) of the input signal by an integer
  factor (call it P).
* applying an FIR (finite-impulse response filter) to the result of 1.
* downsampling (that is, decimation) of the result of 2. by an integer factor
  (call it Q).

License: :ref:`license_upfirdn`.

.. us.example

**Example**

::

    y = upfirdn([0:9], [0.5,1,0.5], 2, 3)  // linear interpolation, rate 2/3
    y -> [0.0 ,  1.0 ,  2.5,  4.0 ,  5.5,  7.0 ,  8.5]

.. us.history

**History**

.. list-table::
   :header-rows: 1

   * - Version
     - Description
   * - R2013.3
     - New.

.. seealso::
   :ref:`overview-mathematic`

:sub:`id-1317927`