Median Absolute Deviation for circular data

[henri laurent]

Hi,

I am looking for a method to measure the variability of a set of angles.

For non circular data, we have bucketizer.mad.

Could we have a bucketizer.mad.circular function the same way we have buckerizer.mean and buckerizer.mean.circular?

Thanks,

Henri

[Fabien Tencé]

Hi Henri,

If you're working with angles, or any data with a modulo applied to it, you should really "unmodulo" it before using the data. This will make most computations a lot easier, including finding the MAD on buckets. At the end of the script, you can just reapply the mod if you need to.

Here is a utility macro I use to "unmodulo" a GTS or a list thereof:

<%

SAVE 'context' STORE

[ 'gts' 'modulo' ] STORE

0 'add_val' STORE

[

$gts

<%

'mw' STORE

$mw 0 GET // Tick

$mw 4 GET -1 GET // Lat

$mw 5 GET -1 GET // Lon

$mw 6 GET -1 GET // Elev

$mw 7 GET -1 GET

$mw 7 GET 0 GET - 'diff' STORE

$diff ABS $modulo 2.0 / >

<%

$diff 0 <

<% $add_val $modulo + 'add_val' STORE %>

<% $add_val $modulo - 'add_val' STORE %>

IFTE

%>

IFT

$mw 7 GET -1 GET $add_val + // Value

%>

1 SNAPSHOTN EVAL

{ 'modulo' $modulo } DEREF

MACROMAPPER

1 0 0

]

MAP

$gts TYPEOF 'LIST' !=

<% 0 GET %>

IFT

$context RESTORE

%>

You can use it this way:

$gtsOrlgts 360 @util/unmod

Regards,

Fabien.