Remap all trajectories to one side (or one quadrant) of the coordinate
system. In doing so, mt_remap_symmetric assumes a centered coordinate
system and a symmetric design of the response buttons (see Details).
mt_remap_symmetric(
data,
use = "trajectories",
save_as = use,
dimensions = c("xpos", "ypos"),
remap_xpos = "left",
remap_ypos = "up"
)a mousetrap data object created using one of the mt_import
functions (see mt_example for details). Alternatively, a trajectory
array can be provided directly (in this case use will be ignored).
a character string specifying which trajectory data should be used.
a character string specifying where the resulting trajectory data should be stored.
a character vector specifying the two dimensions in the trajectory array that contain the mouse positions, the first value corresponding to the x-positions, the second to the y-positions.
character string indicating the direction in which to remap values on the x axis. If set to "left" (as per default), trajectories with an endpoint on the right (i.e. with a positive x-value) will be remapped to the left. The alternatives are "right" which has the reverse effect, and "no", which disables remapping on the horizontal dimension.
character string defining whether tracks directed downwards on the y axis should be remapped so that they end with a positive y value. This will be performed if this parameter is set to "up" (which is the default), and the reverse occurs if the parameter is set to "down". If it is set to "no", y-values remain untouched.
A mousetrap data object (see mt_example) with remapped
trajectories. If the trajectory array was provided directly as data,
only the trajectory array will be returned.
When mouse trajectories are compared across different conditions, it is typically desirable that the endpoints of the trajectories share the same direction (e.g., diagonally up and left). This way, the trajectories can be compared regardless of the button they were directed at.
mt_remap_symmetric can be used to achieve this provided that two
assumptions hold:
First, this function assumes a centered coordinate system, i.e. the coordinate system is centered on the screen center. This is the case when the data is produced by the mousetrap plug-ins in OpenSesame.
Second, it assumes that the response buttons in the mouse-tracking experiment are symmetric, in that they all are equally distant from the screen center.
# Remap trajectories so that all trajectories
# end in the top-left corner
mt_example <- mt_import_mousetrap(mt_example_raw)
mt_example <- mt_remap_symmetric(mt_example)
# Only flip trajectories vertically so that all
# trajectories end in the upper half of the screen
mt_example <- mt_import_mousetrap(mt_example_raw)
mt_example <- mt_remap_symmetric(mt_example,
remap_xpos="no", remap_ypos="up")