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Specifying relative position of text in a plot

11 messages · Tom La Bone, Henrique Dallazuanna, Brian Ripley +4 more

Tom La Bone
# 
What is the simplest way to specify the location of text in a scatter plot
(created using the plot function) in relative terms rather than specific x-y
coordinates? For example, rather than putting text at (300,49) on a plot,
how do I put it 1/10 of the way over from the y axis and 1/2 of the way up
from the x axis? Thanks.

Tom
Henrique Dallazuanna
# 
Try this:

plot(rnorm(100))
text(diff(par("usr")[1:2])/10, sum(par("usr")[3:4])/2, labels="Test")
On 12/03/2008, Tom La Bone <booboo at gforcecable.com> wrote:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Brian Ripley
    

    

      
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See ?par, entry "usr". Either set a new coordinate system and use it, or 
convert 1/10 to user coordinates.

In R-devel (2.7.0 to be) this is easier:

    text(grconvertX(0.1,"npc"), grconvertY(0.5, "npc"), "some text")

cnvrt.coords() in package TeachingDemos does something similar (although 
it doesn't use the standard R names for coordinate systems, and there are 
more than 5).

        
On Wed, 12 Mar 2008, Tom La Bone wrote:

        

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Alberto Monteiro
    

    

      
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Tom La Bone asked:

            

      
      
      
    

        
See the help of par:
?par

Namely:

plot(rnorm(100), rnorm(100))
pu <- par()$usr
x <- pu[1] * 0.5 + pu[2] * 0.5
y <- pu[3] * 0.1 + pu[4] * 0.9
text(x, y, "the quick brown fox jumps over a lazy dog")

Alberto Monteiro

  
  


  


      

    

    

      
      

        


  

        

      Greg Snow
    

    

      
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I tested the main set of examples from cnvrt.coords using the new
grconvert functions and they worked perfectly.  I have already noted in
the help page for cnvrt.coords (for the next version coming out soon)
that people should start using grconvertX and grconvertY when they
become available.

Are there any more of the utilities in TeachingDemos that will be need
to be depricated with the release of version 2.7? (I read through the
current NEWS file, but are there any more planned?).

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Nordlund, Dan (DSHS/RDA)
    

    

      
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This is a useful example of placing text, but I interpreted the request as aking for the text to be placed at the left side of the graph (1/10 of the x range) and centered vertically (with respect to the y scale).  So, then I would calculate x and y as

x <- pu[1] * 0.9 + pu[2] * 0.1
y <- pu[3] * 0.5 + pu[4] * 0.5

Also, text() centers the supplied text at the x,y coordinates. So, if Tom wants the text "begin" at that point, he will need to adjust the x coordinate for the length of the string being printed.

Hope this is helpful,

Dan

Daniel J. Nordlund
Research and Data Analysis
Washington State Department of Social and Health Services
Olympia, WA  98504-5204

  
  


  


      

    

    

      
      

        


  

        

      Greg Snow
    

    

      
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To left justify the text rather than center, use the adj argument, this
is easier and probably more reliable than trying to adjust the x
coordinate manually.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Brian Ripley
    

    

      
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On Wed, 12 Mar 2008, Nordlund, Dan (DSHS/RDA) wrote:

        

            

      
      
      
    

        
Yes, and there has been another wrong answer earlier.  Note that my 
suggestion of

plot(rnorm(100), rnorm(100))
op <- par(usr=c(0,1,0,1))
text(1/10, 1/2, "some text")
par(op)

is a lot less error-prone (and it also works with log scales).

            

      
      
      
    

        
Better, use the adj= argument to text.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Bill Venables
    

    

      
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Here is one way.

...
usr <- par("usr")  		# get user coordinates
par(usr = c(0, 1, 0, 1)) # new relative user coordinates

text(0.1, 0.5, "Some text", adj = 0)  # if that's what you want

par(usr = usr)			# restore original user coordinates

...

If you were going to be doing this a lot, you could write a simple
wrapper function to text(...) to incorporate this change to relative
coordinates and back again.

Bill Venables
CSIRO Laboratories
PO Box 120, Cleveland, 4163
AUSTRALIA
Office Phone (email preferred): +61 7 3826 7251
Fax (if absolutely necessary):  +61 7 3826 7304
Mobile:                         +61 4 8819 4402
Home Phone:                     +61 7 3286 7700
mailto:Bill.Venables at csiro.au
http://www.cmis.csiro.au/bill.venables/ 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Tom La Bone
Sent: Thursday, 13 March 2008 12:34 AM
To: r-help at r-project.org
Subject: [R] Specifying relative position of text in a plot


What is the simplest way to specify the location of text in a scatter
plot
(created using the plot function) in relative terms rather than specific
x-y
coordinates? For example, rather than putting text at (300,49) on a
plot,
how do I put it 1/10 of the way over from the y axis and 1/2 of the way
up
from the x axis? Thanks.

Tom

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Tom La Bone
    

    

      
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Thanks for all of the suggestions. The key key here seems to be using the
"par" function to change the coordinate system like so 

plot(rnorm(100), rnorm(100))
op <- par("usr")
par(usr = c(0, 1, 0, 1))
text(0.5,0.5,"TEST")
par(usr = op)

Prof Ripley commented that this approach will also work on log plots, but I
don't think I completely understand what is going on because this does not
work for me

plot(rlnorm(100), rlnorm(100),log="xy")
op <- par("usr")
par(usr = c(0, 1, 0, 1))
text(0.5,0.5,"TEST")
par(usr = op)

Any hints on what I am doing wrong with the log plots? Thanks again for the
help.

Tom

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Brian Ripley
    

    

      
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On Thu, 13 Mar 2008, Tom La Bone wrote:

        

            

      
      
      
    

        
You need

par(usr = c(0, 1, 0, 1), xlog=FALSE, ylog=FALSE)

to set up a non-log coordinate system.