[R] 'symbols' not plotting correct circle radii

Sarah Goslee sarah.goslee at gmail.com
Wed Jul 18 13:42:13 CEST 2012

On Wed, Jul 18, 2012 at 6:42 AM, Jim Lemon <jim at bitwrit.com.au> wrote:
> On 07/18/2012 08:02 PM, Stuart Leask wrote:
>> Hi there.
>> I have been plotting some circles using 'symbols', with radii representing
>> my data, but the radii looked incorrect.
>> It seems to happen with a single circle too:
>> Symbols ( 0, 0, circles = 40, xlim = c(-40, 40), ylim= c(-40, 40))
>> If I put a ruler up to my monitor (technology!)  to compare the radius
>> with the axes, the circle isn't radius 40; it is closer to 15...
>> I suspect there is a simple answer.
> Hi Stuart,
> The answer does not appear to be simple. While the documentation for symbols
> says that the "inches" argument controls the size of the circles, it appears
> to do so with reference to the user units of the plot, not to that quaint
> unit descending from the twelfth part of someone's foot. So, whatever
> numbers you pass as "circles" seem to be scaled to a maximum dimension of
> whatever "inches" is in user units, at least on the x11 graphics device.

>From ?symbols:

If inches is FALSE, the units are taken to be those of the appropriate axes.

Is that not what's wanted here?


Sarah Goslee

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