R help - Oct 2010 - Pointing to a specific place on the x-axis with an arrow

Hi all,

I am trying to do something simple, but which is deviling me. I want to add an 
up-arrow to the x-axis, pointing to a specific location on the axis. I want the 
arrow to be as large as possible.

Here is where I'm at with my code:

#this part if from the ?plot example:
require(stats)
plot(cars)
lines(lowess(cars))
#I am trying to use mtext to add the arrow... but I don't know how to do it:
mtext("?", side = 1, line = 0, at = 7)
#that question mark is a place-holder for the arrow. How do I put an up-arrow 
there instead of the question mark -- as large as possible?

Many thanks to all of you in advance.
-----------------------------------
Josh Banta, Ph.D
Center for Genomics and Systems Biology
New York University
100 Washington Square East
New York, NY 10003
Tel: (212) 998-8465
http://plantevolutionaryecology.org



      
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On Wed, Oct 6, 2010 at 1:45 AM, Josh B <joshb41 at yahoo.com>
wrote:
> Hi all,
>
> I am trying to do something simple, but which is deviling me. I want to add
an
> up-arrow to the x-axis, pointing to a specific location on the axis. I want
the
> arrow to be as large as possible.
>
> Here is where I'm at with my code:
>
> #this part if from the ?plot example:
> require(stats)
> plot(cars)
> lines(lowess(cars))
> #I am trying to use mtext to add the arrow... but I don't know how to
do it:
> mtext("?", side = 1, line = 0, at = 7)
> #that question mark is a place-holder for the arrow. How do I put an
up-arrow
> there instead of the question mark -- as large as possible?
 Use %up% in an expression - but I think it needs two empty {}
expressions as arguments:

mtext(expression({}%up%{}), side = 1, line = 0, at = 12)

Looks pretty good...

Barry

-- 
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Hi Josh,

Try this...

mtext(expression(symbol("\255")), side=1, line=0, at=7)

Michael


On 6 October 2010 11:45, Josh B <joshb41 at yahoo.com>
wrote:
> Hi all,
>
> I am trying to do something simple, but which is deviling me. I want to add
an
> up-arrow to the x-axis, pointing to a specific location on the axis. I want
the
> arrow to be as large as possible.
>
> Here is where I'm at with my code:
>
> #this part if from the ?plot example:
> require(stats)
> plot(cars)
> lines(lowess(cars))
> #I am trying to use mtext to add the arrow... but I don't know how to
do it:
> mtext("?", side = 1, line = 0, at = 7)
> #that question mark is a place-holder for the arrow. How do I put an
up-arrow
> there instead of the question mark -- as large as possible?
>
> Many thanks to all of you in advance.
> -----------------------------------
> Josh Banta, Ph.D
> Center for Genomics and Systems Biology
> New York University
> 100 Washington Square East
> New York, NY 10003
> Tel: (212) 998-8465
> http://plantevolutionaryecology.org
>
>
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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