Question

Performing a math operation on a value returned by an XQuery

  • 18 October 2013
  • 9 replies
  • 4 views
olivier
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Badge +6
Hi,

 

 

I am using the the following functions for extracting X and Y coordinates values from my geometry:

 

 

<COORD> <X>{geom:get-x-coord()}</X> <Y>{geom:get-y-coord()}</Y> </COORD>

 

 

This works well and  I get something looking like this:

 

 

<?xml version="1.0" encoding="UTF-8"?> <TTSACTION TTSActionId="02A6F0EB5EF98599202DDC830A0000BB"> <CREATEROAD> <LINESTRING> <COORD> <X>4.123456</X> <Y>50.123456</Y> </COORD><COORD> <X>5.789456</X> <Y>49.789456</Y> </COORD><COORD> <X>5.123456</X> <Y>50.456123</Y> </COORD> </LINESTRING>         </CREATEROAD> </TTSACTION>

 

 

However I need to multiply the X and Y values by 10000000 (otherwise I will not be in line with the XSD definitions).

 

 

I tried using the @double() function before multiplying the result by the constant but it is not supported, or at least not in the way I did it.

 

 

It would return the following without performing any calcualtion:

 

 

<?xml version="1.0" encoding="UTF-8"?> <TTSACTION TTSActionId="02A6F0EB5EF98599202DDE4B62000099"> <CREATEROAD> <LINESTRING> <COORD> <X>int(10000000*(double(geom:get-x-coord())))</X> <Y>int(10000000*(double(geom:get-y-coord())))</Y> </COORD><COORD> <X>int(10000000*(double(geom:get-x-coord())))</X> <Y>int(10000000*(double(geom:get-y-coord())))</Y> </COORD><COORD> <X>int(10000000*(double(geom:get-x-coord())))</X> <Y>int(10000000*(double(geom:get-y-coord())))</Y> </COORD> </LINESTRING>         </CREATEROAD> </TTSACTION>

 

 

I must be overlooking something about the syntax. 

 

 

Thanks in advance for your suggestions!

 

 

Best regards,

 

 

Olivier

 

9 replies

david_r
Rank
Userlevel 4
Hi,

 

 

it might be both easier and more transparent if you used an ExpressionEvaluator to multiply the coordinate values.

 

 

David
olivier
Rank
Badge +6
Hi,

 

 

Thanks. Actually I am looking for a solution within the XMLTemplater transformer in order to take advantage from the Geometry Template option which does exactly what I need (looking into the geometry without the need to extract it beforehand). I can call it from the Root part using {geom:process-points( "GEOM" )} and have all the shape point coordinates be returned according to my geometry subtemplate.

 

I know that expressions work well in the ExpressionEvaluator transformer but I don't see how it could be used for this if it is positioned after the XMLTemplator (coordinates are embedded within the XML).

 

 

Best regards,

 

 

Olivier

 

 

takashi
Rank
Userlevel 2
Badge +17
Hi Olivier,

 

 

Since I'm not familiar with XQuery functions, I cannot provide exactly what you need. But, the Scaler transformer (and the CoordinateRounder if necessary) can be used to scale geometries without extracting coordinates. For your information.

 

 

Takashi
fmelizard
Rank
Userlevel 4
Badge +13
Hi Oliver,

 

 

You can try the Xpath numeric operand as described here:

 

http://www.w3.org/TR/xpath-functions/#func-numeric-multiply
olivier
Rank
Badge +6
Hi,

 

 

Thanks to you too Takashi!

 

Using the Scaler transformer (followed by the CoordinateRounder in order to ensure that there is no remaining decimal) is a very creative idea. I just tried it and the only remaining issue with that solution is that my coordinates now appear in scientific notation inside the XML:

 

 

<?xml version="1.0" encoding="UTF-8"?> <TTSACTION TTSActionId="55596A665A55C000202DE58D3E000017"> <CREATEROAD> <LINESTRING> <COORD> <X>4.123456E7</X> <Y>5.0123456E8</Y> </COORD><COORD> <X>5.789456E7</X> <Y>4.9789456E8</Y> </COORD><COORD> <X>5.123456E7</X> <Y>5.0456123E8</Y> </COORD> </LINESTRING>         </CREATEROAD> </TTSACTION>

 

 

I also just tried using the ReplaceString and PadRight FME functions around the {geom:get-x-coord()} and {geom:get-y-coord()} expressions in the XMLTemplator but that doesn't seem to work either.

 

 

In any case, thank you very much for your suggestion!

 

 

Best regards,

 

 

Olivier
olivier
Rank
Badge +6
Hi Itay,

 

 

I have indeed tried using this XQuery function but nothing is being calculated.

 

 

I used the following syntax:

 

 

<COORD> <X>op:numeric-multiply({geom:get-x-coord()},10000000)</X> <Y>op:numeric-multiply({geom:get-y-coord()},10000000)</Y> </COORD>

 

 

It returns:

 

 

<COORD> <X>op:numeric-multiply(4.123456,10000000)</X> <Y>op:numeric-multiply(50.123456,10000000)</Y> </COORD><COORD> <X>op:numeric-multiply(5.789456,10000000)</X> <Y>op:numeric-multiply(49.789456,10000000)</Y> </COORD><COORD> <X>op:numeric-multiply(5.123456,10000000)</X> <Y>op:numeric-multiply(50.456123,10000000)</Y> </COORD>

 

 

Putting the function in between {} does not help either. Do you have any suggestion?

 

 

Thank you!

 

 

Olivier  
fmelizard
Rank
Userlevel 4
Badge +13
Hi Olivier,

 

 

The only suggestion I have, maintaining the data in the XML is to use xfMaps with the XMLFeatureMapper to recreate the point objects and then use the expression evaluator / scaler on them.

 

This wont be my favourite way to do it since xfmaps can be complicated to create and are static.

 

Therefore I would firstly write the xml and then read it with the XML reader using the feature paths to create the geomtries and scale/multiply the coordinate values.

 

Hope this helps,

 

Itay
fmelizard
Rank
Userlevel 4
Badge +13
and , if applicable, scale the objects coordinates BEFORE featching them....
takashi
Rank
Userlevel 2
Badge +17

I found XQuery operators can be used here.

<COORD>
<X>{xs:integer(geom:get-x-coord() * 100000000)}</X>
<Y>{xs:integer(geom:get-y-coord() * 100000000)}</Y>
</COORD>

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