[DDI-users] Documenting rates in the aggregate data extension

[Jostein Ryssevik]

Hi

I am not sure if I understand you correctly, but why cant you use a 
none-additive nCube for this purpose? There will of course always be limits 
to what you can do (software-wise) with none-additive aggregates, but that 
will always be the case independent of the metadata specifications.

If you could include the raw numbers that are used to calculate the rates 
in the cube you would of course be better off, but than you would need a 
way to specify the actual calculation formula. This is missing in the 
current DDI-spec. At least if this is going to provide generic solution a 
simple aggMeth=percent" would not help you much.

Jostein Ryssevik/Nesstar




At 14:50 09.03.2004 +0000, Humphrey Southall wrote:
>The DDI aggregate data extension is very clearly designed to document 
>tables consisting mainly of frequency counts.  What should we do with 
>pre-computed percentages?
>
>My project is converting existing machine-readable transcriptions of 
>tables from British census reports to a structure which uses DDI-based 
>metadata, and most of the columns in those tables are just such counts of 
>numbers of people.
>
>They also contain columns which are pre-computed rates, generally 
>percentages.  Most of them can be derived directly from counts held in 
>other columns in the same table, and so far we have mostly ignored 
>them;  we are not discarding them, as the system will also hold 
>spreadsheet versions of the original tables, but they will not be easily 
>located, or accessible to our visualisation tools.
>
>However, there are some rates in the reports which contain information not 
>available in any other form.  The most immediate issue is with data in the 
>main parish-level table from the 1951 census for England and Wales.  This 
>includes population density, which can easily be computed from figures for 
>population and area, and "Persons per Room", computable from the number of 
>persons and the numbers of rooms in private households.  However, it also 
>includes "Percentage of persons at more than 2 per Room".  Although 
>another table gives plenty of information about numbers of people versus 
>numbers of room, by household, for c. 1,500 districts from which this rate 
>could be computed, no other information is available for the c. 15,000 
>parishes.  The micro-data are official secrets until 2052, and as far as 
>we can establish no unpublished intermediate calculations from pre-1971 
>censuses survive anywhere -- so this is really interesting data.
>
>How can we include these data values in our system?  I can see that just 
>about any number can be held in a non-additive nCube, but that greatly 
>limits what we can do with it.  Is there another structure we should be using?
>
>Best wishes,
>
>Humphrey Southall
> 
>====================================
>Humphrey Southall
>Reader in Geography/Director,
>Great Britain Historical GIS Project
>Department of Geography, University of Portsmouth
>Buckingham Building, Lion Terrace, Portsmouth PO1 3HE
>
>GIS Project Office: (023) 9284 2500
>Home office:  (020) 8853 0396
>
>Web site:       http://www.VisionOfBritain.org.uk
>About us:       http://www.gbhgis.org
>
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Jostein Ryssevik                                        Tel:  +47 5558 2654
Director of Technology and Development                  Mobil: +47 9181 7197
NESSTAR Ltd.                                            http://www.nesstar.com
NESSTAR Ltd is a wholly owned subsidiary of the
UK Data Archive and the Norwegian Social Science Data Services
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