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# Amount of time spent on either side of y-axis

Hi everyone

Is there a way to measure how much time was spent on the left and the right side of the y-axis using mousetrap? I'm almost done with my analysis, but I haven't stumbles upon such a measure yet.

Thanks :)

-Sara

• Hi Sara,

within the mousetrap package, there is no standard measure for that. However, you could compute it with the following code:

```library(mousetrap)

# Use example data from mousetrap package
mt_data <- mt_example

# Compute derivatives to make timestamp differences accessible
mt_data <- mt_derivatives(mt_data, return_delta_time = TRUE)

# Compute time spent for positive x values (i.e., right of y axis)
mt_data\$data\$time_x_positive <- rowSums(mt_data\$trajectories[,,"delta_time"]*(mt_data\$trajectories[,,"xpos"]>0), na.rm = TRUE)

# Compute time spent for negative x values (i.e., left of y axis)
mt_data\$data\$time_x_negative <- rowSums(mt_data\$trajectories[,,"delta_time"]*(mt_data\$trajectories[,,"xpos"]<0), na.rm = TRUE)
```

Note that the time exactly on the y axis (i.e., for x = 0) is excluded. In addition, since you require the time which is a difference measure between two time stamps, it is somewhat arbitrary how these time differences are assigned to the positions (i.e., whether they are shifted forwards or backwards - they are shifted forward within the mt_derivatives function, see documentation: http://pascalkieslich.github.io/mousetrap/reference/mt_derivatives.html#details-1). However, this is just a minor technical detail.

Best,

Pascal