Re: [R] Contour Plot on a non Rectangular Grid
On 10/25/2010 03:30 AM, Lorenzo Isella wrote:
Hello,
I feel I am drowning in a glass of water.
Consider the following snippet at the end of the email, where I
generated a set of {x,y,s=f(x,y)} values, i.e. a set of 2D coordinates +
a scalar on a circle.
Now, I can get a scatterplot in 3D, but how to get a 2D surface
plot/levelplot?
An idea could be to artificially set the z coordinate of the plot as a
constant (instead of having it equal to s as in the scatterplot) and
calculate the colormap with the values of s, along the lines of the
volcano example + surface plot at
http://bit.ly/9MRncd
but I am experiencing problems. However, should I really go through all
this? There is nothing truly 3D in the plot that I have in mind, you can
think of it as e.g. some temperature measurement along a tube cross
section.
Hi Lorenzo,
I'm a bit pressed for time at the moment so I can't write an example,
but why not just define an empty rectangular plot:
plot(0,xlim=your xlimits,ylim=your ylimits,type=n,axes=FALSE,
xlab=,ylab=)
create a matrix of NA values, only calculate the ones that are inside
your shape and display it in the same way that color2D.matplot(plotrix)
does? You should get the shape you want with all of the unwanted cells
blank.
Jim
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Re: [R] Contour Plot on a non Rectangular Grid
On 10/25/2010 01:32 AM, David Winsemius wrote:
You were advised to look at rms. Why have you dismissed this suggestion?
Using your data setup below and packaging into a dataframe.
require(rms)
ddf - datadist(xysf - as.data.frame(xys))
olsfit - ols(V3~rcs(V1,3)+rcs(V2,3), data=xysf)
bounds - perimeter(xysf$V1, xysf$V2)
plot(xysf$V1, xysf$V2) #demonstrates the extent of the data
bplot(Predict(olsfit, V1,V2), perim=bounds) # a levelplot is the default
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot)
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot,
xlim=c(-2.5,2.5))
# to demonstrate that perimeter works
# and as expected this shows very little variability d/t V1
olsfit # note that
anova(olsfit)
Analysis of Variance Response: V3
Factor d.f. Partial SS MS F P
V1 2 0.01618738 8.093691e-03 19.47 .0001
Nonlinear 1 0.01618738 1.618738e-02 38.93 .0001
V2 2 470.67057254 2.353353e+02 566040.95 .0001
Nonlinear 1 470.67057254 4.706706e+02 1132081.91 .0001
TOTAL NONLINEAR 2 527.78127558 2.638906e+02 634723.80 .0001
REGRESSION 4 527.78127558 1.319453e+02 317361.90 .0001
ERROR 7663 3.18594315 4.157566e-04
# most the the regression SS is in the V2 variable
# Q.E.D.
Thanks David,
But I am experiencing some problems with your snippet.
When I run the code at the end of the email (saved as plot_circular.R),
I get the following error
source('plot_circular.R')
Error in value.chk(at, which(name == n), NA, np, lim) :
variable V1 does not have limits defined by datadist
which you clearly do not have on your machine. Have I left out some bits
of your code?
Lorenzo
require(rms)
R - pi/2
n - 100
x - y - seq(-R,R, length=n)
xys - c()
temp - seq(3)
for (i in seq(n)){
for (j in seq(n))
#check I am inside the circle
if ((sqrt(x[i]^2+y[j]^2))=R){
temp[1] - x[i]
temp[2] - y[j]
temp[3] - abs(cos(y[j]))
xys - rbind(xys,temp)
}
}
ddf - datadist(xysf - as.data.frame(xys))
olsfit - ols(V3~rcs(V1,3)+rcs(V2,3), data=xysf)
bounds - perimeter(xysf$V1, xysf$V2)
plot(xysf$V1, xysf$V2) #demonstrates the extent of the data
bplot(Predict(olsfit, V1,V2), perim=bounds) # a levelplot is the default
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot)
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot,
xlim=c(-2.5,2.5))
# to demonstrate that perimeter works
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Re: [R] Contour Plot on a non Rectangular Grid
On Oct 25, 2010, at 3:41 AM, Lorenzo Isella wrote:
On 10/25/2010 01:32 AM, David Winsemius wrote:
You were advised to look at rms. Why have you dismissed this
suggestion?
Using your data setup below and packaging into a dataframe.
require(rms)
ddf - datadist(xysf - as.data.frame(xys))
olsfit - ols(V3~rcs(V1,3)+rcs(V2,3), data=xysf)
bounds - perimeter(xysf$V1, xysf$V2)
plot(xysf$V1, xysf$V2) #demonstrates the extent of the data
bplot(Predict(olsfit, V1,V2), perim=bounds) # a levelplot is the
default
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot)
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot,
xlim=c(-2.5,2.5))
# to demonstrate that perimeter works
# and as expected this shows very little variability d/t V1
olsfit # note that
anova(olsfit)
Analysis of Variance Response: V3
Factor d.f. Partial SS MS F P
V1 2 0.01618738 8.093691e-03 19.47 .0001
Nonlinear 1 0.01618738 1.618738e-02 38.93 .0001
V2 2 470.67057254 2.353353e+02 566040.95 .0001
Nonlinear 1 470.67057254 4.706706e+02 1132081.91 .0001
TOTAL NONLINEAR 2 527.78127558 2.638906e+02 634723.80 .0001
REGRESSION 4 527.78127558 1.319453e+02 317361.90 .0001
ERROR 7663 3.18594315 4.157566e-04
# most the the regression SS is in the V2 variable
# Q.E.D.
Thanks David,
But I am experiencing some problems with your snippet.
When I run the code at the end of the email (saved as
plot_circular.R), I get the following error
source('plot_circular.R')
Error in value.chk(at, which(name == n), NA, np, lim) :
variable V1 does not have limits defined by datadist
which you clearly do not have on your machine. Have I left out some
bits of your code?
Lorenzo
require(rms)
R - pi/2
n - 100
x - y - seq(-R,R, length=n)
xys - c()
temp - seq(3)
for (i in seq(n)){
for (j in seq(n))
#check I am inside the circle
if ((sqrt(x[i]^2+y[j]^2))=R){
temp[1] - x[i]
temp[2] - y[j]
temp[3] - abs(cos(y[j]))
xys - rbind(xys,temp)
}
}
ddf - datadist(xysf - as.data.frame(xys))
# Sorry. There was a single line omitted:
options(datadist=ddf)
olsfit - ols(V3~rcs(V1,3)+rcs(V2,3), data=xysf)
bounds - perimeter(xysf$V1, xysf$V2)
plot(xysf$V1, xysf$V2) #demonstrates the extent of the data
bplot(Predict(olsfit, V1,V2), perim=bounds) # a levelplot is the
default
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot)
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot,
xlim=c(-2.5,2.5))
# to demonstrate that perimeter works
If you do not need a statistical approach to the contour plot, then
Jim Lemon's more recent suggestion this morning may be more economical.
--
David.
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[R] Contour Plot on a non Rectangular Grid
Dear All,
I would like to plot a scalar (e.g. a temperature) on a non-rectangular
domain (or even better: I would simply like to be able to draw a contour
plot on an arbitrary 2D domain). I wonder if there is any tool to
achieve that with R. I did some online search in particular on the list
archives, found several queries similar to this one but was not able to
find any conclusive answer.
I am interested in the following 2 options
(1) just read a file of the form
x1 y1 z1
x2 y2 x2
... ... ...
xn yn zn
where the set of {xi} and {yi} are coordinates on an arbitrary domain
and {zi} are the values of the scalar for the corresponding {x,y}
coordinates.
(2) Sometimes the domain where I want to draw a contour plot is nothing
too fancy and the scalar itself is given by an analytical function.
Consider e.g. the case of a circle of radius R=pi/2 centered about the
origin and a function like
z=f(x,y)=abs(cos(y))
NB: in this case a satisfactory solution could be to plot z on a
rectangular grid and then clip a circular region
To fix the ideas, the final result in this case (with a colorjet map)
should look like this
http://dl.dropbox.com/u/5685598/scalar_plot.pdf
Any suggestion is appreciated.
Many thanks
Lorenzo
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Re: [R] Contour Plot on a non Rectangular Grid
On 24-Oct-10 11:30:57, Lorenzo Isella wrote:
Dear All,
I would like to plot a scalar (e.g. a temperature) on a non-rectangular
domain (or even better: I would simply like to be able to draw a
contour plot on an arbitrary 2D domain). I wonder if there is any
tool to achieve that with R. I did some online search in particular
on the list archives, found several queries similar to this one but
was not able to find any conclusive answer.
I am interested in the following 2 options
(1) just read a file of the form
x1 y1 z1
x2 y2 x2
... ... ...
xn yn zn
where the set of {xi} and {yi} are coordinates on an arbitrary domain
and {zi} are the values of the scalar for the corresponding {x,y}
coordinates.
(2) Sometimes the domain where I want to draw a contour plot is nothing
too fancy and the scalar itself is given by an analytical function.
Consider e.g. the case of a circle of radius R=pi/2 centered about the
origin and a function like
z=f(x,y)=abs(cos(y))
NB: in this case a satisfactory solution could be to plot z on a
rectangular grid and then clip a circular region
To fix the ideas, the final result in this case (with a colorjet map)
should look like this
http://dl.dropbox.com/u/5685598/scalar_plot.pdf
Any suggestion is appreciated.
Many thanks
Lorenzo
For your option (1), the fundamental issue is interpolation.
There are many methods for this, with different proprties!
An R Site Search on interpolation yields a lot of hits.
One (which is fairly basic, but may suit your purposes) is
the interpp() function in package akima:
http://finzi.psych.upenn.edu/R/library/akima/html/interpp.html
Hoping this helps,
Ted.
E-Mail: (Ted Harding) ted.hard...@wlandres.net
Fax-to-email: +44 (0)870 094 0861
Date: 24-Oct-10 Time: 12:51:03
-- XFMail --
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Re: [R] Contour Plot on a non Rectangular Grid
On 10/24/2010 01:51 PM, (Ted Harding) wrote:
On 24-Oct-10 11:30:57, Lorenzo Isella wrote:
Dear All,
I would like to plot a scalar (e.g. a temperature) on a non-rectangular
domain (or even better: I would simply like to be able to draw a
contour plot on an arbitrary 2D domain). I wonder if there is any
tool to achieve that with R. I did some online search in particular
on the list archives, found several queries similar to this one but
was not able to find any conclusive answer.
I am interested in the following 2 options
(1) just read a file of the form
x1 y1 z1
x2 y2 x2
... ... ...
xn yn zn
where the set of {xi} and {yi} are coordinates on an arbitrary domain
and {zi} are the values of the scalar for the corresponding {x,y}
coordinates.
(2) Sometimes the domain where I want to draw a contour plot is nothing
too fancy and the scalar itself is given by an analytical function.
Consider e.g. the case of a circle of radius R=pi/2 centered about the
origin and a function like
z=f(x,y)=abs(cos(y))
NB: in this case a satisfactory solution could be to plot z on a
rectangular grid and then clip a circular region
To fix the ideas, the final result in this case (with a colorjet map)
should look like this
http://dl.dropbox.com/u/5685598/scalar_plot.pdf
Any suggestion is appreciated.
Many thanks
Lorenzo
For your option (1), the fundamental issue is interpolation.
There are many methods for this, with different proprties!
An R Site Search on interpolation yields a lot of hits.
One (which is fairly basic, but may suit your purposes) is
the interpp() function in package akima:
http://finzi.psych.upenn.edu/R/library/akima/html/interpp.html
Hoping this helps,
Ted.
E-Mail: (Ted Harding)ted.hard...@wlandres.net
Fax-to-email: +44 (0)870 094 0861
Date: 24-Oct-10 Time: 12:51:03
-- XFMail --
Hi,
And thanks for helping. I am anyway a bit puzzled, since case (1) is not
only a matter of interpolation. Probably the point I did not make clear
(my fault) is that case (1) in my original email does not refer to an
irregular grid on a rectangular domain; the set of (x,y) coordinate
could stand e.g. a flat metal slab along which I have temperature
measurements. The slab could be e.g. elliptical or any other funny
shape. What also matters is that the final outcome should not look
rectangular, but by eye one should be able to tell the shape of the slab.
Case (1) is a generalization of case (2) where I do not have either an
analytical expression for the surface not for the scalar.
Cheers
Lorenzo
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Re: [R] Contour Plot on a non Rectangular Grid
On 24.10.2010 14:14, Lorenzo Isella wrote:
On 10/24/2010 01:51 PM, (Ted Harding) wrote:
On 24-Oct-10 11:30:57, Lorenzo Isella wrote:
Dear All,
I would like to plot a scalar (e.g. a temperature) on a non-rectangular
domain (or even better: I would simply like to be able to draw a
contour plot on an arbitrary 2D domain). I wonder if there is any
tool to achieve that with R. I did some online search in particular
on the list archives, found several queries similar to this one but
was not able to find any conclusive answer.
I am interested in the following 2 options
(1) just read a file of the form
x1 y1 z1
x2 y2 x2
... ... ...
xn yn zn
where the set of {xi} and {yi} are coordinates on an arbitrary domain
and {zi} are the values of the scalar for the corresponding {x,y}
coordinates.
(2) Sometimes the domain where I want to draw a contour plot is nothing
too fancy and the scalar itself is given by an analytical function.
Consider e.g. the case of a circle of radius R=pi/2 centered about the
origin and a function like
z=f(x,y)=abs(cos(y))
NB: in this case a satisfactory solution could be to plot z on a
rectangular grid and then clip a circular region
To fix the ideas, the final result in this case (with a colorjet map)
should look like this
http://dl.dropbox.com/u/5685598/scalar_plot.pdf
Any suggestion is appreciated.
Many thanks
Lorenzo
For your option (1), the fundamental issue is interpolation.
There are many methods for this, with different proprties!
An R Site Search on interpolation yields a lot of hits.
One (which is fairly basic, but may suit your purposes) is
the interpp() function in package akima:
http://finzi.psych.upenn.edu/R/library/akima/html/interpp.html
Hoping this helps,
Ted.
E-Mail: (Ted Harding)ted.hard...@wlandres.net
Fax-to-email: +44 (0)870 094 0861
Date: 24-Oct-10 Time: 12:51:03
-- XFMail --
Hi,
And thanks for helping. I am anyway a bit puzzled, since case (1) is not
only a matter of interpolation. Probably the point I did not make clear
(my fault) is that case (1) in my original email does not refer to an
irregular grid on a rectangular domain; the set of (x,y) coordinate
could stand e.g. a flat metal slab along which I have temperature
measurements. The slab could be e.g. elliptical or any other funny
shape. What also matters is that the final outcome should not look
rectangular, but by eye one should be able to tell the shape of the slab.
Case (1) is a generalization of case (2) where I do not have either an
analytical expression for the surface not for the scalar.
Cheers
What about the facilities in package rgl then?
Uwe Ligges
Lorenzo
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Re: [R] Contour Plot on a non Rectangular Grid
On Oct 24, 2010, at 4:30 AM, Lorenzo Isella wrote:
Dear All,
I would like to plot a scalar (e.g. a temperature) on a non-
rectangular domain (or even better: I would simply like to be able
to draw a contour plot on an arbitrary 2D domain). I wonder if there
is any tool to achieve that with R. I did some online search in
particular on the list archives, found several queries similar to
this one but was not able to find any conclusive answer.
One implemented approach to this exists with the rms/Hmisc package
combination. The perimeter function is used to define a region within
which the are a sufficient number of cases and the perimeter object is
passed to the bplot function, which is a wrapper for a lattice
contourplot call. There is no reason you couldn't emulate
I am interested in the following 2 options
(1) just read a file of the form
x1 y1 z1
x2 y2 x2
... ... ...
xn yn zn
where the set of {xi} and {yi} are coordinates on an arbitrary
domain and {zi} are the values of the scalar for the corresponding
{x,y} coordinates.
(2) Sometimes the domain where I want to draw a contour plot is
nothing too fancy and the scalar itself is given by an analytical
function. Consider e.g. the case of a circle of radius R=pi/2
centered about the origin and a function like
z=f(x,y)=abs(cos(y))
That defines the contours but does not restrict the domain.
NB: in this case a satisfactory solution could be to plot z on a
rectangular grid and then clip a circular region
To fix the ideas, the final result in this case (with a colorjet
map) should look like this
http://dl.dropbox.com/u/5685598/scalar_plot.pdf
And that color encoded output would not be the output of a contourplot
but is more like a levelplot or an image plot. Nonetheless, the
perimeter and bplot combination can deliver a similar result if you
supply either code or data as a suitable test case for analysis and
display.
__
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] Contour Plot on a non Rectangular Grid
On 10/24/2010 02:55 PM, David Winsemius wrote:
On Oct 24, 2010, at 4:30 AM, Lorenzo Isella wrote:
Dear All,
I would like to plot a scalar (e.g. a temperature) on a
non-rectangular domain (or even better: I would simply like to be able
to draw a contour plot on an arbitrary 2D domain). I wonder if there
is any tool to achieve that with R. I did some online search in
particular on the list archives, found several queries similar to this
one but was not able to find any conclusive answer.
One implemented approach to this exists with the rms/Hmisc package
combination. The perimeter function is used to define a region within
which the are a sufficient number of cases and the perimeter object is
passed to the bplot function, which is a wrapper for a lattice
contourplot call. There is no reason you couldn't emulate
I am interested in the following 2 options
(1) just read a file of the form
x1 y1 z1
x2 y2 x2
... ... ...
xn yn zn
where the set of {xi} and {yi} are coordinates on an arbitrary domain
and {zi} are the values of the scalar for the corresponding {x,y}
coordinates.
(2) Sometimes the domain where I want to draw a contour plot is
nothing too fancy and the scalar itself is given by an analytical
function. Consider e.g. the case of a circle of radius R=pi/2 centered
about the origin and a function like
z=f(x,y)=abs(cos(y))
That defines the contours but does not restrict the domain.
NB: in this case a satisfactory solution could be to plot z on a
rectangular grid and then clip a circular region
To fix the ideas, the final result in this case (with a colorjet map)
should look like this
http://dl.dropbox.com/u/5685598/scalar_plot.pdf
And that color encoded output would not be the output of a contourplot
but is more like a levelplot or an image plot. Nonetheless, the
perimeter and bplot combination can deliver a similar result if you
supply either code or data as a suitable test case for analysis and
display.
I agree that contour plot was a misleading name for what I had in mind.
I'll try your suggestion and the one by Uwe about rgl and post again if
I had troubles. As to the domain of the function, at least in case (1),
that should arise from the collected data points in (x,y) if the
sampling is dense enough.
Cheers
Lorenzo
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Re: [R] Contour Plot on a non Rectangular Grid
On Oct 24, 2010, at 6:12 AM, Lorenzo Isella wrote: As to the domain of the function, at least in case (1), that should arise from the collected data points in (x,y) if the sampling is dense enough. And that is precisely what you get from the perimeter function. The earlier Design package provided an those facilities in base graphics. The paradigm for plotting regression objects changed a bit when Harrell shifted over to Lattice, but he has always provided worked examples that generalize nicely to real situations. There are also som nice examples of contourplots constrained to geographic regions in Woods' text on generalized additive models. I'm sure the spatial stats people have such facilities as well. Cheers Lorenzo __ 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] Contour Plot on a non Rectangular Grid
Hi,
And thanks for helping. I am anyway a bit puzzled, since case (1) is not
only a matter of interpolation. Probably the point I did not make clear
(my fault) is that case (1) in my original email does not refer to an
irregular grid on a rectangular domain; the set of (x,y) coordinate
could stand e.g. a flat metal slab along which I have temperature
measurements. The slab could be e.g. elliptical or any other funny
shape. What also matters is that the final outcome should not look
rectangular, but by eye one should be able to tell the shape of the slab.
Case (1) is a generalization of case (2) where I do not have either an
analytical expression for the surface not for the scalar.
Cheers
What about the facilities in package rgl then?
Uwe Ligges
Hello,
I feel I am drowning in a glass of water.
Consider the following snippet at the end of the email, where I
generated a set of {x,y,s=f(x,y)} values, i.e. a set of 2D coordinates +
a scalar on a circle.
Now, I can get a scatterplot in 3D, but how to get a 2D surface
plot/levelplot?
An idea could be to artificially set the z coordinate of the plot as a
constant (instead of having it equal to s as in the scatterplot) and
calculate the colormap with the values of s, along the lines of the
volcano example + surface plot at
http://bit.ly/9MRncd
but I am experiencing problems. However, should I really go through all
this? There is nothing truly 3D in the plot that I have in mind, you can
think of it as e.g. some temperature measurement along a tube cross section.
Any help is appreciated.
Cheers
Lorenzo
library(scatterplot3d)
library(rgl)
R - pi/2
n - 100
x - y - seq(-R,R, length=n)
xys - c()
temp - seq(3)
for (i in seq(n)){
for (j in seq(n))
#check I am inside the circle
if ((sqrt(x[i]^2+y[j]^2))=R){
temp[1] - x[i]
temp[2] - y[j]
temp[3] - abs(cos(y[j]))
xys - rbind(xys,temp)
}
}
scatterplot3d(xys[,1], xys[,2], xys[,3], highlight.3d=TRUE,
col.axis=blue, col.grid=lightblue,
main=scatterplot3d - 2, pch=20)
#
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Re: [R] Contour Plot on a non Rectangular Grid
On Oct 24, 2010, at 9:30 AM, Lorenzo Isella wrote:
Hi,
And thanks for helping. I am anyway a bit puzzled, since case (1)
is not
only a matter of interpolation. Probably the point I did not make
clear
(my fault) is that case (1) in my original email does not refer to
an
irregular grid on a rectangular domain; the set of (x,y) coordinate
could stand e.g. a flat metal slab along which I have temperature
measurements. The slab could be e.g. elliptical or any other funny
shape. What also matters is that the final outcome should not look
rectangular, but by eye one should be able to tell the shape of
the slab.
Case (1) is a generalization of case (2) where I do not have
either an
analytical expression for the surface not for the scalar.
Cheers
What about the facilities in package rgl then?
Uwe Ligges
Hello,
I feel I am drowning in a glass of water.
Not sure what we are supposed to make of this.
Consider the following snippet at the end of the email, where I
generated a set of {x,y,s=f(x,y)} values, i.e. a set of 2D
coordinates + a scalar on a circle.
Now, I can get a scatterplot in 3D, but how to get a 2D surface plot/
levelplot?
You were advised to look at rms. Why have you dismissed this
suggestion? Using your data setup below and packaging into a dataframe.
require(rms)
ddf - datadist(xysf - as.data.frame(xys))
olsfit - ols(V3~rcs(V1,3)+rcs(V2,3), data=xysf)
bounds - perimeter(xysf$V1, xysf$V2)
plot(xysf$V1, xysf$V2) #demonstrates the extent of the data
bplot(Predict(olsfit, V1,V2), perim=bounds) # a levelplot is the
default
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot)
bplot(Predict(olsfit, V1,V2), perim=bounds, lfun=contourplot,
xlim=c(-2.5,2.5))
# to demonstrate that perimeter works
# and as expected this shows very little variability d/t V1
olsfit # note that
anova(olsfit)
Analysis of Variance Response: V3
Factor d.f. Partial SS MS F P
V1 2 0.01618738 8.093691e-03 19.47 .0001
Nonlinear 1 0.01618738 1.618738e-02 38.93 .0001
V2 2 470.67057254 2.353353e+02 566040.95 .0001
Nonlinear 1 470.67057254 4.706706e+02 1132081.91 .0001
TOTAL NONLINEAR2 527.78127558 2.638906e+02 634723.80 .0001
REGRESSION 4 527.78127558 1.319453e+02 317361.90 .0001
ERROR 7663 3.18594315 4.157566e-04
# most the the regression SS is in the V2 variable
# Q.E.D.
--
David,
An idea could be to artificially set the z coordinate of the plot as
a constant (instead of having it equal to s as in the scatterplot)
and calculate the colormap with the values of s, along the lines of
the volcano example + surface plot at
http://bit.ly/9MRncd
but I am experiencing problems. However, should I really go through
all this? There is nothing truly 3D in the plot that I have in mind,
you can think of it as e.g. some temperature measurement along a
tube cross section.
Any help is appreciated.
Cheers
Lorenzo
library(scatterplot3d)
library(rgl)
R - pi/2
n - 100
x - y - seq(-R,R, length=n)
xys - c()
temp - seq(3)
for (i in seq(n)){
for (j in seq(n))
#check I am inside the circle
if ((sqrt(x[i]^2+y[j]^2))=R){
temp[1] - x[i]
temp[2] - y[j]
temp[3] - abs(cos(y[j]))
xys - rbind(xys,temp)
}
}
scatterplot3d(xys[,1], xys[,2], xys[,3], highlight.3d=TRUE,
col.axis=blue, col.grid=lightblue,
main=scatterplot3d - 2, pch=20)
#
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