I am looking to add patch variable values to a list of empty lists. The patches are divided into different zones, and I'm trying to see how certain patch variables differ by zone.
I have an empty list of lists (actually contains 12 lists, but for simplicity):
set mylist [[] [] [] []]
And a list corresponding to the different zones:
set zone-list [1 2 3 4]
Here's how I'm trying to build the lists:
(foreach mylist zone-list [set ?1 lput (sum-zone-variable ?2) ?1])
to-report sum-zone-variable [ n ]
report (sum [patch-variable] of patches with [zone = n])
end
When I run this, mylist stays empty (ie unchanged). I think the problem is with the foreach statement, but I can't figure out what it is. Any help?
I can see the thinking behind foreach mylist [ set ?1 ... ], but NetLogo doesn't work that way. set ?1 ... has no effect on the original list. NetLogo lists are immutable, and ?1 is not a reference to an updatable location in a list — it's just a temporary variable into which a value has been copied. So set ?1 ... is something you will basically never write.
If I understand your question correctly, the relevant primitive here is map. This should do the job:
set mylist (map [lput (sum-zone-variable ?2) ?1] mylist zonelist)
Your basic approach is ok except that you must assign to a name. E.g.,
globals [mylist zone-list n-zones]
patches-own [zone zone-variable]
to setup
set n-zones 4
set zone-list n-values n-zones [?]
ask patches [set zone one-of zone-list]
set mylist n-values n-zones [[]]
end
to go
ask patches [set zone-variable random-float 1]
foreach zone-list [
let total sum [zone-variable] of patches with [zone = ?]
let oldvals item ? mylist
set mylist replace-item ? mylist (lput total oldvals)
]
end
However, you might want to use the table extension for this.
