Re: [R] plot scale

2009-10-02 Thread Greg Snow
Here is a different approach:
This example uses the default plotting device, but should work the same with 
postscript or any other device.  Just set the size of the paper to a standard 
size, or a large enough size to fit your largest plot:

dev.new()
tmp <- par('plt')

scale <- 5
x <- runif(100, 0, 20)
y <- rnorm(100, x)

dx <- diff(range(x))*1.08
wx <- grconvertX(dx/scale, from='inches', to='ndc')

dy <- diff(range(y))*1.08
wy <- grconvertY(dy/scale, from='inches', to='ndc')

par(plt = c(tmp[1], tmp[1]+wx, tmp[3], tmp[3]+wy) )
plot(x,y)

dev.new()

x2 <- runif(100, 0,5)
y2 <- rnorm(100, x2)

dx <- diff(range(x2))*1.08
wx <- grconvertX(dx/scale, from='inches', to='ndc')

dy <- diff(range(y2))*1.08
wy <- grconvertY(dy/scale, from='inches', to='ndc')

par(plt = c(tmp[1], tmp[1]+wx, tmp[3], tmp[3]+wy) )
plot(x2,y2)


The above only works for 1 plot per page (no layout or par(mfrow=... ) ).

This keeps the lower left corner of the plot in the same place (so change the 
margins before the call to par('plt') if you want them different). Then sets 
the top and right parts of the plotting region leaving white space on the top 
and right to get the scaling correct (you will have problems if your desired 
scale does not fit in the window/on the page).  This example uses a "scale" of 
5 plot units per inch, change as appropriate.  The *1.08 is to account for the 
extra area that is added to the plot by default, change this for the other axis 
type.

Hope this helps,



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


> -Original Message-
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-
> project.org] On Behalf Of Ben Kenward
> Sent: Friday, October 02, 2009 2:08 AM
> To: r-help@r-project.org
> Subject: [R] plot scale
> 
> Hi,
> 
> Is there a way to set the scale of a plot (i.e. number of axis units
> per centimeter) when you output it to postscript? If not, how am I
> supposed to plot graphs with different axis limits to the same scale?
> They just get resized to fit the paper so that graphs which show a
> smaller number of axis units end up with a larger scale.
> 
> Cheers,
> 
> Ben
> 
> --
> Dr. Ben Kenward
> Department of Psychology, Uppsala University, Sweden
> http://www.benkenward.com
> 
> __
> R-help@r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

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Re: [R] plot scale

2009-10-02 Thread Ryan
> 
> Hi,
> 
> Is there a way to set the scale of a plot (i.e. number of axis units
> per centimeter) when you output it to postscript? If not, how am I
> supposed to plot graphs with different axis limits to the same scale?
> They just get resized to fit the paper so that graphs which show a
> smaller number of axis units end up with a larger scale.
> 
> Cheers,
> 
> Ben
> 

If I understand you correctly, you want the units on each axis to 
be physically represented equally on the same scale.  If this is right, 
try using the lattice package (xyplot, etc.) with aspect="iso".

Lattice lets you adjust the aspect ratio of the plot to whatever you 
like and constrains the dimensions of the plot accordingly.  Base 
graphics also allow for control of the aspect ratio using "asp=", but 
extend the limits of the plot to fill whatever region you are plotting 
in.

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Re: [R] plot scale

2009-10-02 Thread baptiste auguie
Hi,

It looks like lattice or ggplot2 might make this easier, but I'm not
entirely sure I understood the problem, short of an example.

Best,

baptiste

2009/10/2 Duncan Murdoch :
> On 02/10/2009 4:07 AM, Ben Kenward wrote:
>>
>> Hi,
>>
>> Is there a way to set the scale of a plot (i.e. number of axis units
>> per centimeter) when you output it to postscript? If not, how am I
>> supposed to plot graphs with different axis limits to the same scale?
>> They just get resized to fit the paper so that graphs which show a
>> smaller number of axis units end up with a larger scale.
>
> I don't think there's a simple way to specify the exact relationship, but
> you can do it with some work.
>
> When you open the postscript device, you can specify the size.  When you do
> a plot, you can specify the size of the margins, so that lets you indirectly
> specify the size of the plot region.  And of course you can specify the axis
> limits.
>
> So the way I'd do what you want is as follows:  plot the data, use
> par("usr") to extract the axis limits, use par("mai") to extract the margin
> size.  Then calculate the size you want for the particular scaling, and open
> the postscript device with that size, reset par("mai") to the previous
> value, and repeat your plot.
>
> Duncan Murdoch
>
> __
> R-help@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.
>

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Re: [R] plot scale

2009-10-02 Thread Ben Kenward
On Fri, Oct 2, 2009 at 11:10 AM, Duncan Murdoch  wrote:
> I don't think there's a simple way to specify the exact relationship, but
> you can do it with some work.

Thanks Duncan. That's what I was beginning to suspect, nice to have
confirmation, even if it will mean a bit of work.

Ben

-- 
Dr. Ben Kenward
Department of Psychology, Uppsala University, Sweden
http://www.benkenward.com

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Re: [R] plot scale

2009-10-02 Thread Duncan Murdoch

On 02/10/2009 4:07 AM, Ben Kenward wrote:

Hi,

Is there a way to set the scale of a plot (i.e. number of axis units
per centimeter) when you output it to postscript? If not, how am I
supposed to plot graphs with different axis limits to the same scale?
They just get resized to fit the paper so that graphs which show a
smaller number of axis units end up with a larger scale.


I don't think there's a simple way to specify the exact relationship, 
but you can do it with some work.


When you open the postscript device, you can specify the size.  When you 
do a plot, you can specify the size of the margins, so that lets you 
indirectly specify the size of the plot region.  And of course you can 
specify the axis limits.


So the way I'd do what you want is as follows:  plot the data, use 
par("usr") to extract the axis limits, use par("mai") to extract the 
margin size.  Then calculate the size you want for the particular 
scaling, and open the postscript device with that size, reset par("mai") 
to the previous value, and repeat your plot.


Duncan Murdoch

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[R] plot scale

2009-10-02 Thread Ben Kenward
Hi,

Is there a way to set the scale of a plot (i.e. number of axis units
per centimeter) when you output it to postscript? If not, how am I
supposed to plot graphs with different axis limits to the same scale?
They just get resized to fit the paper so that graphs which show a
smaller number of axis units end up with a larger scale.

Cheers,

Ben

-- 
Dr. Ben Kenward
Department of Psychology, Uppsala University, Sweden
http://www.benkenward.com

__
R-help@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.