[R] identifying what labels have been created in a plot

[Marc Schwartz]

on 01/30/2009 10:51 AM Dennis Fisher wrote:
> Colleagues
> 
> R 2.8.0; OS X, Vista, Ubuntu Linux
> 
> In some instances, when I create a graphic using plot(XVAR, YVAR), it
> would be valuable to know the values that R will display on the y-axis
> (e.g., if the range of data is 0-70, it might display 0, 10, 30, 50,
> 70).   Is there a simple means to access these values?
> 
> Also, in some instances, additional ticks appear between the displayed
> values (in this case, at 20, 40, 60).  Can I obtain the list of the
> positions of all ticks?
> 
> Access to this information permits me to tailor the ticks and labels in
> a particular manner.
> 
> Thanks for any suggestions.
> 
> Dennis

See ?axis, where in the Details, it will lead you to ?axTicks

plot(c(0, 70), c(0, 70))

# Y axis tick marks
> axTicks(2)
[1]  0 10 20 30 40 50 60 70


pretty() will also get you similar information, save when using log scaling:

> pretty(c(0, 70))
[1]  0 10 20 30 40 50 60 70


Keep in mind that you can always explicitly call axis() using the 'at'
argument to specify the locations of the tick marks and labels, after
plotting something without the axes being drawn by default.

HTH,

Marc Schwartz