====Downsample====

The **Downsample** function is part of the [[histhelper|HistoryFill]] class.

It's used to //decrease the amount of data transmitted// to the ARDI server by summarising and/or aggregating data points.

This allows users to query large time-periods of data without overwhelming the network or server.

Generally, this should done in the **data source** wherever possible (ie. using an SQL statement with 'GROUP BY', choosing an aggregation method in your query etc.).

However, informal systems rarely have easy ways to perform this sort of task - the //Downsample// function is used in these situations.

===Parameters===

The function takes one parameter...

^Parameter^Type^Description^
|Addresses|array|A list of strings, containing the addresses for each point to be resampled|

===Warning===

This function is only for use on **analogue** data points. Do not use this function on discrete (ie. on/off) data.

===Example===

<code python>

#Record all of the points, building a list of the names as we go...
pointnamelist = []
for p in allpoints:
   if p.name not in pointnamelist:
      pointnamelist.append(p.name)
   history.RecordAnalogue(p.name,p.time,p.value)

#Upscale the low-resolution data
history.Downsample(pointnamelist)
</code>

===See Also===

You can also do the opposite job - [[Upsample]] is used to //increase// the resolution of your data.

[[Autosample]] is used to automatically choose if up or down-sampling is appropriate.