From: Marc Schwartz <marc_schwartz_at_me.com>

Date: Tue, 15 Jun 2010 14:35:54 -0500

>>> -----Original Message-----

*>>> From: r-help-bounces_at_r-project.org
*

*>>> [mailto:r-help-bounces_at_r-project.org] On Behalf Of
*

*>>> Ted.Harding_at_manchester.ac.uk
*

*>>> Sent: Tuesday, June 15, 2010 8:49 AM
*

*>>> To: r-help_at_stat.math.ethz.ch
*

*>>> Subject: [R] Unspecified [upper] xlim/ylim?
*

*>>>
*

*>>> Greetings!
*

*>>> I would like to be able to specify a fixed (say) lower limit
*

*>>> for plotting, while leaving the upper limit "floating, when
*

*>>> plotting. The context is that the maximum in the data to be
*

*>>> plotted is unpredictable, being the consequence of a simulation,
*

*>>> whereas I know that it cannot be less than (say) 0; and I want
*

*>>> to fix the lower limit at 0 in any plot, leaving the upper limit
*

*>>> to be assigned by plot() as a result of the computed values.
*

*>>>
*

*>>> I know I can do this by determining the max() of the data, and
*

*>>> then computing a "Ymax" to put in (say) ylim = c(0,Ymax). However,
*

*>>> for certain reasons, I would prefer not to have to do this.
*

*>>> (And it's just a preference ... ).
*

*>>>
*

*>>> Whereas one can leave the whole issue of setting both plotting
*

*>>> limits to plot(), by not specifying ylim (or xlim), or one can
*

*>>> explcitily specify both the upper and lower limits by (say)
*

*>>> ylim=c(Ymin,Ymax), there seems to be no way of fixing one and
*

*>>> leaving the other floating so that plot() would do its own thing.
*

*>>>
*

*>>> ylim requires two numbers to be given. Things like ylim=c(0,)
*

*>>> or ylim=c(0,NA) would generate an error.
*

*>>>
*

>>> Am I chasing a phantom? Or is there a way?

*>>> Thanks
*

*>>> Ted.
*

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. Received on Tue 15 Jun 2010 - 19:39:02 GMT

Date: Tue, 15 Jun 2010 14:35:54 -0500

On Jun 15, 2010, at 12:11 PM, Ted Harding wrote:

> On 15-Jun-10 16:01:24, William Dunlap wrote:

>>> -----Original Message-----

>> >> Currently ylim=c(yValueAtBottomOfPlot, yValueAtTopOfPlot), not >> c(yMin,yMax). E.g., ylim=c(10,0) means to reverse the y axis, >> with 0 at the top and 10 at the bottom. Putting an NA into >> ylim seems attractive but doesn't it run into problems because >> ylim doesn't mean c(yMin,yMax)? >> >> Bill Dunlap >> Spotfire, TIBCO Software >> wdunlap tibco.com >>

>>> Am I chasing a phantom? Or is there a way?

> > Sorry, Bill, but you've misunderstood what I mean by "Ymin" and "Ymax". > As explained, these are notations for values which I either compute, > or choose, to put in as the arguments in ylim=c(... , ...). YMin and > Ymax would be such as to ensure that the range of the axis included > at least the range (Ymin,Ymax) (or, depending on the choice, possibly > to exclude certain values from the plot). > > So, indeed, ylim does mean c(Ymin,Tmax). > > Ted.

Ted, perhaps I am being dense here (always a possibility), but by default if, for example, 'ylim' is unspecified, plot() essentially uses range(YVals) as the min/max values for the Y axis. Also, by default, with par(yaxs = "r"), the Y axis range is extended by 4% in both directions. Same for the x axis range.

Here is the snippet of relevant code from plot.default() for 'ylim':

ylim <- if (is.null(ylim))

range(xy$y[is.finite(xy$y)])

else ylim

Thus, if you want to explicitly specify the low end of the range for the Y axis and have the upper end of the range left to the default methodology, you would indeed use:

ylim = c(0, max(YVals))

as the argument syntax. The same would apply for the x axis limits.

Is that what you are after?

**HTH,
**
Marc Schwartz

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. Received on Tue 15 Jun 2010 - 19:39:02 GMT

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