The data stem from a 2x2-factorial design where both factors have two levels. The x-axis shows the words of a sentence and the y-axis the mean reaction time for each single word. Here is how I visualize the data so far with base R:

enter image description here

I find the usual method of visualizing such data rather unappealing but I couldn't come up with a nice idea myself. Are there more appropriate ways of summarizing such data in one single plot?

  • $\begingroup$ What are the bars above and below the points? What are the stars? They need to be described or removed. Why is the axis broken when there are no points below the break, and the scale doesn't seem to actually break there? $\endgroup$ Feb 28, 2015 at 13:25
  • $\begingroup$ And if there's any kind of natural (read: substantively relevant) ordering on the x-axis, you should use it. BTW I'm posting these as comments and not answers because they don't really relate to 2x2 experiments, but I think they do need to be addressed $\endgroup$ Feb 28, 2015 at 13:29
  • $\begingroup$ The bars are error bars according to Cosineau (2005). The stars show significance but don't really matter here as this is random data. The scale with the original data is broken between 0 and a larger number. In short: This is a pure dumb plot only in existence to illustrate the problem without a lot of words. It obviously lacks the precision one would wish for. $\endgroup$ Feb 28, 2015 at 13:34
  • $\begingroup$ my suggestion stands: label it or drop it. Also, don't break plots just to get 0 in there, unless 0 is an important reference point for this data (and usually it isn't) $\endgroup$ Feb 28, 2015 at 14:08
  • $\begingroup$ I agree with the labeling but error bars et. al. I would outsource to a figure caption. The breaking-the-axis-part is controversial so we probably won't settle this here. Thanks for the tips. $\endgroup$ Feb 28, 2015 at 14:12

1 Answer 1


The X-axis is not a continuous variable, therefore connecting the adjacent X-values is not appropriate. In other words: ditch the connecting lines.

As for visualisation, one other option would be to use a bar chart. But I am afraid it would only make things worse.

IMHO, the best visualization would actually be to put the values in a table. One word in a row with your four values as columns.

  • $\begingroup$ "The X-axis is not a continuous variable, therefore connecting the adjacent X-values is not appropriate." I completely disagree. $\endgroup$ Feb 28, 2015 at 13:22
  • 2
    $\begingroup$ But I do agree that a table is a great idea. $\endgroup$ Feb 28, 2015 at 13:23
  • $\begingroup$ There is nothing prohibiting you from connecting the dots with lines, but the clarity of such visualisation is very poor. Just look at that graph from the Wiki page that you linked - you have to look it from a distance to see some patterns... $\endgroup$
    – alesc
    Feb 28, 2015 at 13:26
  • $\begingroup$ Call it preference, then. But try drawing that graph without the connecting lines: good luck seeing any patterns at all. $\endgroup$ Feb 28, 2015 at 13:28
  • $\begingroup$ I don't see the table-"plot" to be a viable option. Regarding the bar-chart-option: A bar chart were you put four bars for each word next to each other? $\endgroup$ Feb 28, 2015 at 14:19

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