Marc-Olivier The simplest solution - in the sense that most packages could handle it - is to carry out a 'nested' indicator analysis.
That is: (i) code one of your particle classes as '1' and all other as '0', produce a map of proportion of this class. (ii) remove this particle class from your data. Code the next class as 1 and all others as 0. produce a map of "the proportion of this class, given that it is not in the first class". The 'actual' proportion is then P(ii)*(1-P(i)). (iii) If you have more than three classes, you can keep nesting although you tend to run out of data pretty fast. The last class has whatever proportion is left. Proportions such as this which have to add up to 1 or 100% have been the subject of a lot of study, particularly by people such as Vera Pawlowsky-Glahn under the title 'compositional data'. Isobel http://geoecosse.bizland.com/BYOGeostats.htm ___________________________________________________________ALL-NEW Yahoo! Messenger - sooooo many all-new ways to express yourself http://uk.messenger.yahoo.com
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