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Mouse trap - what is RT.x and RT.y?

Hi all

I'm using mousetrap to analyse data collected using MouseTracker.

I've created measures with the mt_measures command, but when I merge this into my mousetrap object (which I've called mt_data), the resulting data frame doesn't report just RT, but two RT variables, RT.x and RT.y. The variable RT is there prior to the merge in mt_data$data$RT.

To merge the measures and data, I've used the command:

mt_data <- dplyr::inner_join(mt_data$data,




Output of summary to show that RT.x and RT.y are rather different

> summary (mt_data$RT.x)

  Min. 1st Qu. Median   Mean 3rd Qu.   Max.

   950   1700   1910   1971   2180   3470

> summary (mt_data$RT.y)

  Min. 1st Qu. Median   Mean 3rd Qu.   Max.

   450   1150   1560   1533   1870   3430

I've searched through the .pdf for reference to these measures but it doesn't appear to be there.

Would it be okay to combine these two measures to give an overall RT of the trial length with something like:

rt_total <- (mt_data$RT.x + mt_data$RT.y)/2

Or do they represent such different things that merging them back together in this way is nonsensical (e.g. if I were to feed this through to an ANOVA)?

Note: the measure RT.x/y is not present in either my mt_data$data or mt_data$measures prior to the merge.


  • edited June 2019

    Hi there,

    you already have correctly identified the source of the issue :) . Because there is one RT variable in mt_data$data and one RT variable in mt_data$measures, the dplyr::inner_join function adds a .x to the variable from the first dataset (mt_data$data) and a .y to the variable from the second dataset (mt_data$measures).

    RT.x is the RT variable from MouseTracker, RT.y the RT variable calculated by the mt_measures function. So depending on which of these variables you would like to use, you should either use RT.x or RT.y (but you should not combine them).

    I actually don't know why the variables differ, i.e., I don't know how specifically MouseTracker determines its RT variable. mt_measures determines the RT as the timestamp of the last recorded coordinate.



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