The simplest solution - in the sense that most
packages could handle it - is to carry out a 'nested'
(i) code one of your particle classes as '1' and all
other as '0', produce a map of proportion of this
(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
(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
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'.
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