# The resample operator

The resample operator is a very advanced operator changing the sample times of the data.
The resample operator is very useful if you wants to combine two data sets having unequal sampling rates.

As an example suppose you in igr wants to plot one quantity (q1) versus another (q0).
However if the two quantities have unequal sampling rates this is not possible. Then you can do in the calculator:

```v0 = resample(q0,q1)
p0x = v0
p0y = q1
```
The resample(q0,q1) put the resampled q0 data into v0 with the same sample times as the q1 data.

Below is the Help file from the operator, (author S.W.) :

```RESAMPLE OPERATOR v 1.0
=======================

1st June 2001
S.W.

This note briefly describes the ISDAT operator 'resample' that may be
used to resample a data set at another sampling rate or to resample
one data set using the time tags of a second dataset. The operator
provides re-sampling using either linear interpolation or averaging
using weights defined by a square or Bartlett window.

The software is based upon the methods described by C.Harvey and
S.Schwartz, in Analysis methods for Multi-Spacecraft Data,
eds. G.Paschmann and P.Daly, ISSI Scientific Report SR-001.

Calculator Command Interface
----------------------------
The resample operator is accessed from the calculator facility within
IGR and processes IGR quantities that have already been defined.
The operator requires 2 input arguments and generates a new quantity.

Two forms of the calculator command are possible.
If both arguments refer to the same data quantity

e.g.
v0=resample(q0, q0)

a new set of time tags will be generated and the data object q0 will
be re-sampled using the new time tags. The sampling rate of the new
time tags will be taken from the current operator parameter settings
which are set using the GUI interface (see below).

The second form of the command

v0=resample(q0, q1)

will resample the first data object using the time tags taken from
the second data object.

The method used for the re-sampling is defined be the current operator
parameter settings which may be set using the operator graphical interface.

Graphical User Interface
------------------------
The graphical user interface for the re-sampling operator is activated
by selecting the operator name in the calculator command text box and
choosing Edit->Operator from the main menu.

Using the GUI, the user may select one of the various methods to be
applied to the data and set the output sampling frequency. NOTE that
the output sampling frequency is only required if both input arguments
are the same.

The buttons and the bottom of the window perform the following tasks

OK       Exits window
Cancel   Exits window
Help     Activates the pop-up help window
```

Updated Aug 15, 2006 by B. L.