[R] Implementing trees in R
Hi all, I am rather new to R. Recently I have been trying to implement some tree algorithms in R. I used lists to model tree nodes. I thought something like this would work: parent - list(); child - list(); parent$child1 - child; child$parent - parent; When I tried to check whether a node is its parent's first child using if (node$parent$child1 == node), it always returned false. Then I realized that it does not really work because parent$child1 - child actually makes a copy of child instead of referencing it. I think one possible fix is to keep a list of node objects, and make references using the positions in the list. For example, I think the following would work: parent - list(); child - list(); nodes - list(parent, child); parent$child1 - 2; child$parent - 1; Then the first child test can be rewritten as if (nodes[[nodes[[nodeId]]$parent]]$child1 == nodeId). However, I would prefer not to implement trees in this way, as it requires the inconvenient and error-prone manipulations of node IDs. May I know if there is a way to make object references to lists? Or are there other ways to implement tree data structures in R? BTW, I checked how hclust was implemented, and noticed that it calls an external Fortran program. I would want a solution not involving any external programs. Thanks. -- God bless. Kevin __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Implementing trees in R
Hi Gabor, Thanks for the suggestions. I tried to look for the proto vignette document but could not find it, could you tell me how to reach it? Besides, is it possible to define my own node object type with a default behavior for the - operator of its member variables being referencing rather than copying? Any good reference material/ similar code examples? Thanks. Gabor Grothendieck wrote: Lists are not good for this. There is an example in section 3.3 of the proto vignette of using proto objects for this. That section also references an S4 example although its pretty messy with S4. You might want to look at the graph, RBGL and graphviz packages in Bioconductor and the dynamicgraph, mathgraph and sna packages on CRAN. On 3/16/07, Yuk Lap Yip (Kevin) [EMAIL PROTECTED] wrote: Hi all, I am rather new to R. Recently I have been trying to implement some tree algorithms in R. I used lists to model tree nodes. I thought something like this would work: parent - list(); child - list(); parent$child1 - child; child$parent - parent; When I tried to check whether a node is its parent's first child using if (node$parent$child1 == node), it always returned false. Then I realized that it does not really work because parent$child1 - child actually makes a copy of child instead of referencing it. I think one possible fix is to keep a list of node objects, and make references using the positions in the list. For example, I think the following would work: parent - list(); child - list(); nodes - list(parent, child); parent$child1 - 2; child$parent - 1; Then the first child test can be rewritten as if (nodes[[nodes[[nodeId]]$parent]]$child1 == nodeId). However, I would prefer not to implement trees in this way, as it requires the inconvenient and error-prone manipulations of node IDs. May I know if there is a way to make object references to lists? Or are there other ways to implement tree data structures in R? BTW, I checked how hclust was implemented, and noticed that it calls an external Fortran program. I would want a solution not involving any external programs. Thanks. -- God bless. Kevin __ R-help@stat.math.ethz.ch 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. -- God bless. Kevin __ R-help@stat.math.ethz.ch 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] Implementing trees in R
Gabor,
Thanks. That helps a lot.
Gabor Grothendieck wrote:
On 3/16/07, Gabor Grothendieck [EMAIL PROTECTED] wrote:
1. Here is your example redone using proto:
library(proto)
parent - proto()
child - proto(a = 1)
parent$child1 - child
child$parent.env - parent
This last line should have been:
parent.env(child) - parent
# also just for illustration lets change a
parent$child1$a # 1
child$a - 2
parent$child1$a # 2
2. To redefine $- use S3 or S4 but it can be done
in conjunction with proto like this:
# constructor
node - function(. = parent.frame(), ...)
structure(proto(...), class = c(node, proto))
$-.node - function(this, s, value) {
if (s == .super)
parent.env(this) - value
if (is.function(value))
environment(value) - this
if (inherits(value, node))
parent.env(value) - this
this[[as.character(substitute(s))]] - value
this
}
p - node(a = 1)
p$child - node(b = 2)
p$child$parent.env()
p # same
On 3/16/07, Yuk Lap Yip (Kevin) [EMAIL PROTECTED] wrote:
Hi Gabor,
Thanks for the suggestions. I tried to look for the proto vignette
document but could not find it, could you tell me how to reach it?
Besides, is it possible to define my own node object type with a
default behavior for the - operator of its member variables being
referencing rather than copying? Any good reference material/ similar
code examples?
Thanks.
Gabor Grothendieck wrote:
Lists are not good for this. There is an example in section 3.3 of
the proto vignette of using proto objects for this. That section
also references an S4 example although its pretty messy with S4.
You might want to look at the graph, RBGL and graphviz packages
in Bioconductor and the dynamicgraph, mathgraph and sna packages
on CRAN.
On 3/16/07, Yuk Lap Yip (Kevin) [EMAIL PROTECTED] wrote:
Hi all,
I am rather new to R. Recently I have been trying to
implement some
tree algorithms in R. I used lists to model tree nodes. I thought
something like this would work:
parent - list();
child - list();
parent$child1 - child;
child$parent - parent;
When I tried to check whether a node is its parent's first child
using if (node$parent$child1 == node), it always returned
false. Then
I realized that it does not really work because parent$child1
- child
actually makes a copy of child instead of referencing it. I
think one
possible fix is to keep a list of node objects, and make references
using the positions in the list. For example, I think the following
would work:
parent - list();
child - list();
nodes - list(parent, child);
parent$child1 - 2;
child$parent - 1;
Then the first child test can be rewritten as if
(nodes[[nodes[[nodeId]]$parent]]$child1 == nodeId). However, I
would
prefer not to implement trees in this way, as it requires the
inconvenient and error-prone manipulations of node IDs.
May I know if there is a way to make object references to
lists? Or
are there other ways to implement tree data structures in R?
BTW, I checked how hclust was implemented, and noticed that
it calls
an external Fortran program. I would want a solution not
involving any
external programs.
Thanks.
--
God bless.
Kevin
__
R-help@stat.math.ethz.ch 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.
--
God bless.
Kevin
--
God bless.
Kevin
__
R-help@stat.math.ethz.ch 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.
