R help - Mar 2010 - image() function

Hello.

I would like to know how to set the image() function so that it assigns 
colors 
relative to an absolute scale, as opposed to relative to the values 
present 
in a particular call to image(). 

For example: 

m <- matrix(1:18,3,6)

par(mfrow = c(2,1))
image(1:6, 1:3, t(m), col = rainbow(20))
image(1:6, 1:3, t(m+9), col = rainbow(20))

Then the two images are identical.  But the right half of the first matrix 

coincides (numerically) with the left half of the second.   (i.e. compare 
'm' and 'm+9'.)

So the question is: how can image() (or some other function) assign the 
same color to every incidence of any given value across repeated calls 
to image()?

Thanks in advance.

JH


 
**************************************************************************************************************

PRIVATE & CONFIDENTIAL: This email and any files transmitted with it are
confidential. Any unauthorized use of the information contained in t
his email or its attachments is prohibited.  If this email is received in error,
please contact the sender and delete the material from your
computer systems. Do not use, copy, or disclose the contents of this email or
any attachments.

Abu Dhabi Investment Authority (ADIA) does not enter into contracts or provide
undertakings by email.  ADIA accepts no responsibility for the
 content of this mail to the extent that it is unrelated to its activities or
the same consists of statements or opinions  which are the send
er's own and not made on behalf of ADIA.  ADIA does not accept any liability
for any errors or omissions in the content of this email caused
by electronic and technical failures. Although ADIA has taken reasonable
precautions to ensure that no viruses are present in this email, ADI
A accepts no responsibility for any loss or damage arising from the use of this
email or its attachments.

**************************************************************************************************************

	[[alternative HTML version deleted]]

Use the zlim argument to image:

m <- matrix(1:18,3,6)

par(mfrow = c(2,1))
image(1:6, 1:3, t(m), col = rainbow(20), zlim=c(0,30))
image(1:6, 1:3, t(m+9), col = rainbow(20), zlim=c(0,30))

hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Jorge Hernandez
> Sent: Friday, March 26, 2010 4:21 AM
> To: r-help at r-project.org
> Subject: [R] image() function
> 
> Hello.
> 
> I would like to know how to set the image() function so that it assigns
> colors
> relative to an absolute scale, as opposed to relative to the values
> present
> in a particular call to image().
> 
> For example:
> 
> m <- matrix(1:18,3,6)
> 
> par(mfrow = c(2,1))
> image(1:6, 1:3, t(m), col = rainbow(20))
> image(1:6, 1:3, t(m+9), col = rainbow(20))
> 
> Then the two images are identical.  But the right half of the first
> matrix
> 
> coincides (numerically) with the left half of the second.   (i.e.
> compare
> 'm' and 'm+9'.)
> 
> So the question is: how can image() (or some other function) assign the
> same color to every incidence of any given value across repeated calls
> to image()?
> 
> Thanks in advance.
> 
> JH
> 
> 
> 
> ***********************************************************************
> ***************************************
> 
> PRIVATE & CONFIDENTIAL: This email and any files transmitted with it
> are confidential. Any unauthorized use of the information contained in
> t
> his email or its attachments is prohibited.  If this email is received
> in error, please contact the sender and delete the material from your
> computer systems. Do not use, copy, or disclose the contents of this
> email or any attachments.
> 
> Abu Dhabi Investment Authority (ADIA) does not enter into contracts or
> provide undertakings by email.  ADIA accepts no responsibility for the
>  content of this mail to the extent that it is unrelated to its
> activities or the same consists of statements or opinions  which are
> the send
> er's own and not made on behalf of ADIA.  ADIA does not accept any
> liability for any errors or omissions in the content of this email
> caused
> by electronic and technical failures. Although ADIA has taken
> reasonable precautions to ensure that no viruses are present in this
> email, ADI
> A accepts no responsibility for any loss or damage arising from the use
> of this email or its attachments.
> 
> ***********************************************************************
> ***************************************
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.