Re: [R] question on contour function
Duncan and David, thank you so much.
You are right. We can use
z1 - outer(x, y, function(x,y) x^2+3*y^2)
rather than
xy - meshgrid(x,y)
z2 - xy$x^2+ 3*xy$y^2
to get right answer. I run these codes on my computer and found that z2 is
the transpose of z1.
So I guess in order to obtain the expected result, there are at least two
ways.
x - seq(-1,1,0.1)
y - seq(-1,1,0.1)
z - outer(x,y, FUN=function(x,y) x^2+ 3*y^2)
contour(x,y,z,col=blue,xlab=x,ylab=y)
or
require(RTOMO)
x - seq(-1,1,0.1)
y - seq(-1,1,0.1)
xy - meshgrid(x,y)
z - xy$x^2+ 3*xy$y^2
z - t(z)
contour(x,y,z,col=blue,xlab=x,ylab=y)
Of course, the first method is better since it only uses the base function.
David Lee
On 12 August 2010 01:54, David Winsemius dwinsem...@comcast.net wrote:
On Aug 11, 2010, at 11:16 AM, ba ba wrote:
Dear All,
I tried to plot contour lines using R function contour, but got the
results
which are not expected.
require(RTOMO)
x - seq(-1,1,0.1)
y - seq(-1,1,0.1)
xy - meshgrid(x,y)
z - xy$x^2+ 3*xy$y^2
contour(x,y,z,col=blue,xlab=x,ylab=y)
The above code gave me the contour graph for z=3*x^2+y^2 rather than
z=x^2+3*y^2. Is anyone know the reason?
Because contour was expecting a matrix of z values for z and you gave it a
list created by a function you did not understand?
meshgrid
function (a, b)
{
return(list(x = outer(b * 0, a, FUN = +), y = outer(b,
a * 0, FUN = +)))
}
Instead:
Use the base function outer():
x - seq(-1,1,0.1)
y - seq(-1,1,0.1)
xy - outer(x,y, FUN=function(x,y) x^2+ 3*y^2)
contour(x,y,xy,col=blue,xlab=x,ylab=y)
--
David Winsemius, MD
West Hartford, CT
[[alternative HTML version deleted]]
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[R] question on contour function
Dear All, I tried to plot contour lines using R function contour, but got the results which are not expected. require(RTOMO) x - seq(-1,1,0.1) y - seq(-1,1,0.1) xy - meshgrid(x,y) z - xy$x^2+ 3*xy$y^2 contour(x,y,z,col=blue,xlab=x,ylab=y) The above code gave me the contour graph for z=3*x^2+y^2 rather than z=x^2+3*y^2. Is anyone know the reason? Thank you very much in advance. David [[alternative HTML version deleted]] __ 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.
Re: [R] question on contour function
On 11/08/2010 11:16 AM, ba ba wrote: Dear All, I tried to plot contour lines using R function contour, but got the results which are not expected. require(RTOMO) x - seq(-1,1,0.1) y - seq(-1,1,0.1) xy - meshgrid(x,y) z - xy$x^2+ 3*xy$y^2 contour(x,y,z,col=blue,xlab=x,ylab=y) The above code gave me the contour graph for z=3*x^2+y^2 rather than z=x^2+3*y^2. Is anyone know the reason? Thank you very much in advance. A problem in RTOMO, or a misuse of it? If I do the calculation of z as z - outer(x, y, function(x,y) x^2+3*y^2) I get the expected result. 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.
Re: [R] question on contour function
On Aug 11, 2010, at 11:16 AM, ba ba wrote:
Dear All,
I tried to plot contour lines using R function contour, but got the
results
which are not expected.
require(RTOMO)
x - seq(-1,1,0.1)
y - seq(-1,1,0.1)
xy - meshgrid(x,y)
z - xy$x^2+ 3*xy$y^2
contour(x,y,z,col=blue,xlab=x,ylab=y)
The above code gave me the contour graph for z=3*x^2+y^2 rather than
z=x^2+3*y^2. Is anyone know the reason?
Because contour was expecting a matrix of z values for z and you gave
it a list created by a function you did not understand?
meshgrid
function (a, b)
{
return(list(x = outer(b * 0, a, FUN = +), y = outer(b,
a * 0, FUN = +)))
}
Instead:
Use the base function outer():
x - seq(-1,1,0.1)
y - seq(-1,1,0.1)
xy - outer(x,y, FUN=function(x,y) x^2+ 3*y^2)
contour(x,y,xy,col=blue,xlab=x,ylab=y)
--
David Winsemius, MD
West Hartford, CT
__
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.
