[solved] output cursor x and y and targets

psukar

Hi all,

I've been piloting a Corsi blocks study and I was confident it was working, participants have to watch a block sequence play out and then tap out the same sequence on the tablet.

in the output it give me cursor x and cursor y values, which I assumed was the 'tap' coordinates on the screen. But these dont seem to match the target coordinates for the block positions at all. For a start all the cursor values are positive and some of my blocks are at negative co-ordinates.

Do the two columns work on different measurements? I'm pretty sure after testing that it is picking up the taps correctly, i.e. inside the target it registers 1 or correct and outside it registers incorrect or 0.

Any ideas?

Thanks,
Kat x

psukar

C:\Users\psukar\Dropbox\Katherine, Julia, Helen, shared folder\Battery One\Corsi and Digit Span Tasks\Screenshot 2014-04-09 19.35.58.png

sebastiaan

Hi,

It is a bit counterintuitive, but the coordinate systems that are used are indeed different. The sketchpad uses the center of the screen as (0, 0), whereas for mouse coordinates (0, 0) corresponds to the top-left.

See also:

• http://osdoc.cogsci.nl/python/mouse/

You can quite easily correct for this, though. You will see a column width in your log file. If you add subtract 0.5*width to cursor_x you will have the coordinates relative to the center. And the same for height and cursor_y.

Hope this helps!

Cheers,
Sebastiaan

psukar

Thank you so much, I'm going to have a look at doing that now. I have another post on here about a stopping rule which I'm trying to upload an image for so people can see my layout, I dont suppose you've seen it? Its kinda very imminent problem I have at the moment and I'm kind of at a loss for how to fix to, I wouldn't even know where to start if I'm honest as I think my experiment has an unusual response input / format. I've tried to explain everything in the post,

Thank you again,
Katherine.

psukar

Did you mean subtract in the above answer?

Edwin

Yes, I think Sebastiaan meant to substract.

Examples (all based on a resolution of 1024x768):

Top left is (0,0) in mouse coordinates, but (-512,-384) in sketchpad coordinates. To transform mouse to sketchpad, simply substract half of the width from the x, and half of the height of the y coordinate: 0 - (1024/2) = -512 and 0 - (768/2) = -384.

Bottom right is (1024, 768) in mouse coordinates, but (512,384) in sketchpad coordinates. 1024 - (1024/2) = 512 and 768 - (768/2) = 384

Centre is (512,384) in mouse coordinates, but (0,0) in sketchpad coordinates. 512 - (1024/2) = 0 and 384 - (768/2) = 0