From: Deepayan Sarkar <deepayan.sarkar_at_gmail.com>

Date: Tue, 20 May 2008 11:34:12 -0700

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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 20 May 2008 - 18:43:51 GMT

Date: Tue, 20 May 2008 11:34:12 -0700

On 5/20/08, Joshua Hertlein <jhertlein_at_hotmail.com> wrote:

*>
*

> Hello,

*>
**> I am very interested in "banking to 45 degrees" as defined by William S. Cleveland
**> in "Visualizing Data." I like to do it in R as well as Excel, etc. With R I have come
**> across the following method:
**>
**> xyplot(x, y, aspect="xy") (part of "lattice" package)
**>
**> which will bank my graph to 45 degrees. My question is how do I obtain the
**> aspect ratio that banks this graph to 45 degrees? I understand that R does it
**> for me, but I would like to explicitly know the aspect ratio so that I can configure
**> other graphs in Excel or other software.
*

*> foo <- xyplot(sunspot.year ~ 1700:1988, type = "l", aspect = "xy")
**> foo$aspect.ratio
*

[1] 0.04554598

> aspect ratio = v / h (v is vertical distance of plot, h is horizontal distance of plot.

*> NOT in the data units, but true, actual distance).
**>
**> I've also come across "banking ()", but I don't understand it, nor the significance
**> of the value it returns. Regardless, it doesn't seem to be the aspect ratio that
**> I am looking for.
*

banking(dx, dy) basically gives you the median of abs(dy/dx). The idea is that dx and dy define the slopes of the segments you want to bank (so typically, dx = diff(x) and dy = diff(y) if x and y are the data you want to plot). banking() gives you a single (summary) slope; you then choose the aspect ratio of your plot so that this slope (in the data coordinates) has a physical slope of 1. To do this, you solve an equation involving the data range in the x- and y-axes of your plot.

-Deepayan

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