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identifying what labels have been created in a plot

4 messages · Dennis Fisher, Marc Schwartz, jim holtman +1 more

#
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


Dennis Fisher MD
P < (The "P Less Than" Company)
Phone: 1-866-PLessThan (1-866-753-7784)
Fax: 1-415-564-2220
www.PLessThan.com
#
on 01/30/2009 10:51 AM Dennis Fisher wrote:
See ?axis, where in the Details, it will lead you to ?axTicks

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

# Y axis tick marks
[1]  0 10 20 30 40 50 60 70


pretty() will also get you similar information, save when using log scaling:
[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
#
It might be easier to generate the plot without the y-axis and then
add you data with 'axis' using whatever tick marks you want.
On Fri, Jan 30, 2009 at 11:51 AM, Dennis Fisher <fisher at plessthan.com> wrote:

  
    
#
You might want to look at the pretty function. The code that I have  
seen often calls that function for the creation of axis tick levels  
with min and max as arguments. And its help page suggests that axTicks  
may give you exactly what you were seeking.