I think you want to do the sum of squared differences between a constant and a list of numbers, where the list of numbers is the value of Z for several turtles. If this is correct, then the following is a complete model that does what you want.
turtles-own [ varZ ]
to setup
clear-all
create-turtles 40
[ setxy random-xcor random-ycor
set varZ random 10
set color blue
]
testme
end
to testme
ask one-of turtles
[ set color red
let friends other turtles in-radius 4
ask friends [ set color yellow ]
type "my varZ is: " print varZ
type "sum of squared differences is: " print sum-sq-diff varZ [varZ] of friends
]
end
to-report sum-sq-diff [#constant #listvals]
report reduce + (map [ thisval -> (thisval - #constant) ^ 2 ] #listvals)
end
The procedure sum-sq-diff takes two inputs: a constant and a list of values. It calculates the squared sum of differences between the constant and each value in the list. The map does the square of differences and creates a list of those values, then the reduce sums across the list. You can test is by simply typing sum-sq-diff 1 [ 2 3 4 ] in the command centre and you will get back 14 (which is (2-1)^2 + (3-1)^2 + (4-1)^2).
The rest of the code is an example of how to use this procedure in the context I think you want, pulling out the turtles within some radius and using their variable values as the list.
