I have a set of agents called 'trees', which have an attribute 'species' that is a string, e.g. 'species1', 'species2', 'species3' etc.
When the trees have fruits, they are blue. When they have no fruits, they are red.
I want to be able to get the number of different species that have trees with fruits at any different step of my model. I can use the following observer command to get an output that describes the species of each tree with fruits:
ask trees with [color != red] [show species]
However this will return something like
(tree 1) 'species 1'
(tree 18) 'species 3'
(tree 24) 'species 1'
(tree 30) 'species 5'
How can I turn this into something which can count the number of different species that have trees which have fruit? In the above example, it would return 3 (as trees of 'species 1', 'species 3', and 'species 5' still have fruit on them).
The ideal output would therefore be
3
I'd like just a number as this will feed into an equation to make a variable that effects they next timestep of the simulation.
That's an interesting question...
One possibility:
a) Create a list with the species of all the trees: let species-list [species] of trees
b) Remove the duplicate values on that list: set species-list remove-duplicates species-list
c) Count how many (unique) species are now on the list: let num-species length species-list
Give it a try!