Hello all,

I am designing an experiment with the builder to present 80 images on different locations on a 360-degree wheel. Then I want participants to choose the correct location of the image with a mouse click on that wheel. I know I can take the mouse position as an output. However, I need to give immediate feedback about the angle difference between the correct location and participants’ responses.

As far as I can see, the solution seems to be adding polygons and give feedback based on whether the mouse click is on the correct polygon or not. However, I am trying to obtain a continuous measure, and it seems exhaustive to add 360 polygons…

I am adding a short clip of the current experiment: pyexp.mov - Google Drive

I will appreciate any suggestions. Thank you

No, the solution is trigonometry . The centre of the screen (and I guess the centre of your circle) are the origin at (0, 0). So it is easy to use the x, y coordinates of the mouse to work out an angle relative to the origin. From SOHCAHTOA, you know that the tangent of the angle is O/A, or y/x in this case. So take the inverse tangent of that to return the angle:

```
response_angle = np.arctan(mouse.pos[1]/mouse.pos[0])
```

The angle will be in radians so you might want to use `rad2deg(response_angle)`

to convert to degrees. Also bear in mind that PsychoPy stimuli I think use a convention where 0 is at 12 o’clock and angles run clockwise, whereas the `numpy`

(imported as `np`

) module functions I think use the standard mathematical convention of anti-clockwise angles starting from 3 o’clock.

Your instincts here are correct - whenever the solution seems to involve lots of duplication, it is almost certainly an indication that a snippet or more of code is required instead.

Thanks a lot for your kind response. It was extremely helpful! If anyone is interested in further discussion about my experiment, I would be happy to!