By Diane - 7/2/2014
Hi,
I have four picture elements that randomly select an item from an item element. However, I noticed that sometimes an item is selected more than once, even though I used the "noreplace" attribute. How can I randomly select without replacement?
This is the relevant part of the code:
<item recallcues>
</item>
<trial fillrecallcues>
/ontrialbegin = [item.recallcues.item=item.poweritems1.1;
item.recallcues.item=item.indexitems2.1;
item.recallcues.item=item.fingeritems3.1;
item.recallcues.item=item.parallelitems4.1]
/ trialduration = 0
</trial>
<picture recallcue1>
/items = recallcues
/select = noreplace
/size = (20%,20%)
/ position = (10,10)
</picture>
<picture recallcue2>
/items = recallcues
/select = noreplace
/size = (20%,20%)
/ position = (30,10)
</picture>
<picture recallcue3>
/items = recallcues
/select = noreplace
/size = (20%,20%)
/ position = (50,10)
</picture>
<picture recallcue4>
/items = recallcues
/select = noreplace
/size = (20%,20%)
/ position = (70,10)
</picture>
Thanks,
Diane
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By Dave - 7/2/2014
See e.g. https://www.millisecond.com/forums/FindPost13609.aspx.
What you need to realize is that having several stimulus elements (<text>, <picture>) reference the same <item> element
<picture recallcue1>
/items = recallcues
/select = noreplace
/size = (20%,20%)
/ position = (10,10)
</picture>
<picture recallcue2>
/items = recallcues
/select = noreplace
/size = (20%,20%)
/ position = (30,10)
</picture>...
does *not* establish a single selection pool for all those stimulus elements. They are independent and each one will sample from *all* the items given in the <item> element without replacement. I.e.
<text text1> / items = myitems / select = noreplace ... </text>
<text text2> / items = myitems / select = noreplace ... </text>
<item myitems> / 1 = "A" / 2 = "B" / 3 = "C" / 4 = "D" </item>
is equivalent to stating
<text text1> / items = ("A", "B", "C", "D") / select = noreplace ... </text>
<text text2> / items = ("A", "B", "C", "D") / select = noreplace ... </text> |
By Diane - 7/3/2014
Hi Dave
Thanks. That link doesnt seem to work, but perhaps my question can be solved in a different way.
The reason I have made 4 recallcue picture elements is that I want four pictures at four different locations on the screen, and which picture goes where should be random. Is there a way to do that with one picture element?
Thanks
Diane |
By Dave - 7/3/2014
And, yes, of course that's possible:
<trial mytrial> / stimulusframes = [1=t1,t2,t3,t4] / validresponse = (57) </trial> <text t1> / items = myitems / position = (20%, 50%) / select = list.mylist.nextvalue </text> <text t2> / items = myitems / position = (40%, 50%) / select = list.mylist.nextvalue </text> <text t3> / items = myitems / position = (60%, 50%) / select = list.mylist.nextvalue </text> <text t4> / items = myitems / position = (80%, 50%) / select = list.mylist.nextvalue </text> <item myitems> / 1 = "A" / 2 = "B" / 3 = "C" / 4 = "D" </item> <list mylist> / items = (1,2,3,4) / selectionrate = always </list>
(works the same for <picture> elements). |
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