Thanks again Dave.
I feel you are teaching the village idiot how to fish rather than throwing him a fish and I appreciate this.
I assume you indicate with the red text that these are the redundant entries. I just don't see what you mean by the same position multiple times.
If I give my narrative of how I understand it to work, you may see where my thinking is awry.
Using your hints, my current code runs correctly over ten tests for just two of the images, however as soon as I extend it to three pictures collisions abound.
<counter type1xpos>
/ items = (25.0000%,25.0001%,75.0000%,75.0001%)
/ select = noreplace
</counter>
<counter type1ypos>
/ items = (25.0000%,75.0000%,25.0000%,75.0000%)
/ select = current(type1xpos)
</counter>
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Candidate positions for pic2 stimuli (all positions but *not* the
one already chosen for pic1 stimulus)
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
<counter type2xpos>
/ items = (25.0001%,25.0001%,75.0001%,75.0001%)
/ not = (type1xpos,type1ypos)
/ select = noreplace
/ selectionrate = always
</counter>
<counter type2ypos>
/ items = (75.0000%,75.0000%,25.0000%,25.0000%)
/ not = (type1ypos,type1xpos)
/ select = current(type2xpos)
/ selectionrate = always
</counter>
CORRECTION: Testing again, there were collisions.
If I just leave the items in red, not understanding why they don't create the same position multiple times, I get collisions even more frequently.
I am wandering blind and just throwing my line in without really knowing how to bait the hook as I am simply not getting this basic concept of creating unique positions.
I have tried introducing new positions to strive for 'different' positions, eg 25.0003 and 25.0004 etc., but this doesn't appear to work either.
Also I am not getting how the select = current(type2xpos) works.
When I look at the example in the documentation,
<text vicepresidents>
/ items =
vicepresidentitems
/ select = current(presidents)
</text>
The following first selects Jefferson, then Adams, and then Washington:
<text presidents>
/ items = ("George Washington",
"John Adams", "Thomas Jefferson")
/ select = sequence(3, 2,
1)
</text>
my understanding is that the vicepresidentitems would look something like:
<text vicepresidents>
<items = ( "Adams", "Jefferson","Burr")
</text>
Hence at first choice, current(presidents) returns 3, this then is the selection from vicepresidentlist, #3 - Burr ?
So extending this to picking a vposition after choosing a hposition, if say 25.001 was chosen at the second position, then
/select = current(type2xpos), looks for the second choice in the list, say 75% in the above example, ignoring for the moment the red text.
Is that correct?
I can't rationally proceed until I know if I am on the right track with this or totally lost at sea.
Any life lines handy Dave?
Patrick
(Thanks for the explanation on the floating point representations, that made sense.)