Dear friends, I was drawing a circle with centrum in (1,-1) and radius 5 to show my girl that the line y=3*x+1 goes through (1,4) and (-2,-5) of the circle, but on Windows XP, R 2.20 the drawing was not good at all, and the known solutions were not shown in the graph. I guess I got it wrong? Is this use not intended ? Best wishes Troels Ring, MD Aalborg, Denmark symbols(x=1,y=-1,circles=5,inches=FALSE, xlim=c(-10,10),ylim=c(-10,10)) curve(3*x+1,-10,10,1000,add=T) abline(v=c(-2,1)) abline(h=c(-1,-5,4))
Hi Troels Ring wrote:> Dear friends, I was drawing a circle with centrum in (1,-1) and > radius 5 to show my girl that the line y=3*x+1 goes through (1,4) and > (-2,-5) of the circle, but on Windows XP, R 2.20 the drawing was not > good at all, and the known solutions were not shown in the graph. I > guess I got it wrong? Is this use not intended ? > > Best wishes > Troels Ring, MD > Aalborg, Denmark > > symbols(x=1,y=-1,circles=5,inches=FALSE, xlim=c(-10,10),ylim=c(-10,10)) > curve(3*x+1,-10,10,1000,add=T) > abline(v=c(-2,1)) > abline(h=c(-1,-5,4))The important part may be that your plot is not square. In the help file for symbols() it says (NOTE the "x axis") ... inches: If 'inches' is 'FALSE', the units are taken to be those of the x axis. If you precede your code with ... par(pty="s") ... does the result look better? Paul -- Dr Paul Murrell Department of Statistics The University of Auckland Private Bag 92019 Auckland New Zealand 64 9 3737599 x85392 paul at stat.auckland.ac.nz http://www.stat.auckland.ac.nz/~paul/
Troels Ring wrote:> Dear friends, I was drawing a circle with centrum in (1,-1) and > radius 5 to show my girl that the line y=3*x+1 goes through (1,4) and > (-2,-5) of the circle, but on Windows XP, R 2.20 the drawing was not > good at all, and the known solutions were not shown in the graph. I > guess I got it wrong? Is this use not intended ? > > Best wishes > Troels Ring, MD > Aalborg, Denmark > > symbols(x=1,y=-1,circles=5,inches=FALSE, xlim=c(-10,10),ylim=c(-10,10)) > curve(3*x+1,-10,10,1000,add=T) > abline(v=c(-2,1)) > abline(h=c(-1,-5,4)) >Hi, Troels, The aspect ratio of y to x is not 1. So, the symbol is visually a circle but in reality an ellipse. Try symbols(x = 1, y = -1, circles = 5, inches = FALSE, asp = 1, xlim = c(-10, 10), ylim = c(-10, 10)) curve(3 * x + 1, -10, 10, 1000, add = TRUE) abline(v = c(-2, 1)) abline(h = c(-1, -5, 4)) HTH, --sundar
?symbols says
inches: If 'inches' is 'FALSE', the units are taken to be
those of
the x axis.
Note, 'the x axis' and you have not ensured the x and y axes have the
same
scale. Try
plot(c(-10,10), c(-10,10), asp=1, type="n")
symbols(x=1,y=-1,circles=5,inches=FALSE, add=TRUE
curve(3*x+1,-10,10,1000,add=TRUE)
abline(v=c(-2,1))
abline(h=c(-1,-5,4))
which works for me. (eqscplot in MASS is another way to do this.)
On Tue, 29 Nov 2005, Troels Ring wrote:
> Dear friends, I was drawing a circle with centrum in (1,-1) and
> radius 5 to show my girl that the line y=3*x+1 goes through (1,4) and
> (-2,-5) of the circle, but on Windows XP, R 2.20 the drawing was not
> good at all, and the known solutions were not shown in the graph. I
> guess I got it wrong? Is this use not intended ?
>
> Best wishes
> Troels Ring, MD
> Aalborg, Denmark
>
> symbols(x=1,y=-1,circles=5,inches=FALSE, xlim=c(-10,10),ylim=c(-10,10))
> curve(3*x+1,-10,10,1000,add=T)
> abline(v=c(-2,1))
> abline(h=c(-1,-5,4))
>
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--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595