Re: [R] Force evaluation of a symbol when a function is created
Here's one more way. It seems to me this is the most R-like way to do
what you want:
multiply_by_Y - function(Y) {
force(Y)
function(x) x*Y
}
F - multiply_by_Y(3)
The force call forces Y to be evaluated at that point, so its value is
fixed from that point forward.
Duncan Murdoch
On 12-08-06 5:07 PM, Schoenfeld, David Alan,Ph.D.,Biostatistics wrote:
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't arguments
are evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can easily
simulate the Matlab behavior. I know that I can live without this in ordinary
programming but it would make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
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Re: [R] Force evaluation of a symbol when a function is created
Duncan, et.al:
Many thanks: let the closure do the work automatically rather than
manually manipulating it.
However, in the spirit of the OP's original request, I believe the
call would be:
Y - 3 ## That is, Y gets a value at some prior point, perhaps
programmatically.
F - multiply_by_Y(Y) # ... F picks up this value implicitly -- no need
for explicit assignment.
But then there is no need for force(), is there?
fy - function(Y)function(x) x*Y
Y - 2
F - fy(Y)
F(5)
[1] 10
Y - 3
F(5)
[1] 10
G - fy(Y)
G(5)
[1] 15
That is, one simply relies on lexical scoping/closures to retain the
value of Y used as a free variable in function(x)x*Y when it is
defined. No need to explicitly force() it. If wrong, I would be
grateful for correction. This appears to me to duplicate the Matlab
behavior rather closely.
-- Bert
On Tue, Aug 7, 2012 at 3:48 AM, Duncan Murdoch murdoch.dun...@gmail.com wrote:
Here's one more way. It seems to me this is the most R-like way to do what
you want:
multiply_by_Y - function(Y) {
force(Y)
function(x) x*Y
}
F - multiply_by_Y(3)
The force call forces Y to be evaluated at that point, so its value is
fixed from that point forward.
Duncan Murdoch
On 12-08-06 5:07 PM, Schoenfeld, David Alan,Ph.D.,Biostatistics wrote:
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't
arguments are evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can
easily simulate the Matlab behavior. I know that I can live without this in
ordinary programming but it would make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
__
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.
__
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.
--
Bert Gunter
Genentech Nonclinical Biostatistics
Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
__
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] Force evaluation of a symbol when a function is created
On 12-08-07 10:46 AM, Bert Gunter wrote:
Duncan, et.al:
Many thanks: let the closure do the work automatically rather than
manually manipulating it.
However, in the spirit of the OP's original request, I believe the
call would be:
Y - 3 ## That is, Y gets a value at some prior point, perhaps
programmatically.
F - multiply_by_Y(Y) # ... F picks up this value implicitly -- no need
for explicit assignment.
But then there is no need for force(), is there?
You still need force:
fy - function(Y)function(x) x*Y
Y - 2
F - fy(Y)
Y - 3
F(5)
This will print 15, because F only contains a promise to evaluate Y, it
hasn't been evaluated until the very last line, and by that time Y has
been changed to 3.
If you are going to construct functions in functions, and their results
depend on the arguments to the constructor, then it's almost always a
good idea to force the arguments. Sometimes it isn't necessary (the
value will be forced implicitly), and in some rare circumstances you
might want to capture the promise instead of its value, but it's
generally a good idea. It is a fairly cheap operation.
Duncan Murdoch
fy - function(Y)function(x) x*Y
Y - 2
F - fy(Y)
F(5)
[1] 10
Y - 3
F(5)
[1] 10
G - fy(Y)
G(5)
[1] 15
That is, one simply relies on lexical scoping/closures to retain the
value of Y used as a free variable in function(x)x*Y when it is
defined. No need to explicitly force() it. If wrong, I would be
grateful for correction. This appears to me to duplicate the Matlab
behavior rather closely.
-- Bert
On Tue, Aug 7, 2012 at 3:48 AM, Duncan Murdoch murdoch.dun...@gmail.com wrote:
Here's one more way. It seems to me this is the most R-like way to do what
you want:
multiply_by_Y - function(Y) {
force(Y)
function(x) x*Y
}
F - multiply_by_Y(3)
The force call forces Y to be evaluated at that point, so its value is
fixed from that point forward.
Duncan Murdoch
On 12-08-06 5:07 PM, Schoenfeld, David Alan,Ph.D.,Biostatistics wrote:
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't
arguments are evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can
easily simulate the Matlab behavior. I know that I can live without this in
ordinary programming but it would make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
__
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.
__
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.
__
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Force evaluation of a symbol when a function is created
Thanks Duncan. That clarifies it!
-- Bert
On Tue, Aug 7, 2012 at 12:28 PM, Duncan Murdoch
murdoch.dun...@gmail.com wrote:
On 12-08-07 10:46 AM, Bert Gunter wrote:
Duncan, et.al:
Many thanks: let the closure do the work automatically rather than
manually manipulating it.
However, in the spirit of the OP's original request, I believe the
call would be:
Y - 3 ## That is, Y gets a value at some prior point, perhaps
programmatically.
F - multiply_by_Y(Y) # ... F picks up this value implicitly -- no
need for explicit assignment.
But then there is no need for force(), is there?
You still need force:
fy - function(Y)function(x) x*Y
Y - 2
F - fy(Y)
Y - 3
F(5)
This will print 15, because F only contains a promise to evaluate Y, it
hasn't been evaluated until the very last line, and by that time Y has been
changed to 3.
If you are going to construct functions in functions, and their results
depend on the arguments to the constructor, then it's almost always a good
idea to force the arguments. Sometimes it isn't necessary (the value will
be forced implicitly), and in some rare circumstances you might want to
capture the promise instead of its value, but it's generally a good idea.
It is a fairly cheap operation.
Duncan Murdoch
fy - function(Y)function(x) x*Y
Y - 2
F - fy(Y)
F(5)
[1] 10
Y - 3
F(5)
[1] 10
G - fy(Y)
G(5)
[1] 15
That is, one simply relies on lexical scoping/closures to retain the
value of Y used as a free variable in function(x)x*Y when it is
defined. No need to explicitly force() it. If wrong, I would be
grateful for correction. This appears to me to duplicate the Matlab
behavior rather closely.
-- Bert
On Tue, Aug 7, 2012 at 3:48 AM, Duncan Murdoch murdoch.dun...@gmail.com
wrote:
Here's one more way. It seems to me this is the most R-like way to do
what
you want:
multiply_by_Y - function(Y) {
force(Y)
function(x) x*Y
}
F - multiply_by_Y(3)
The force call forces Y to be evaluated at that point, so its value is
fixed from that point forward.
Duncan Murdoch
On 12-08-06 5:07 PM, Schoenfeld, David Alan,Ph.D.,Biostatistics wrote:
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't
arguments are evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can
easily simulate the Matlab behavior. I know that I can live without
this in
ordinary programming but it would make my port much easier.
Thanks.
The information in this e-mail is intended only for the
...{{dropped:14}}
__
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.
__
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.
--
Bert Gunter
Genentech Nonclinical Biostatistics
Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
__
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.
[R] Force evaluation of a symbol when a function is created
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't arguments
are evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can easily
simulate the Matlab behavior. I know that I can live without this in ordinary
programming but it would make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
__
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] Force evaluation of a symbol when a function is created
You could use local(), as in
F - local({
+Y - 3
+function(x) x * Y
+})
F(7)
[1] 21
Y - 19
F(5)
[1] 15
Look into 'environments' for more.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf
Of Schoenfeld, David Alan,Ph.D.,Biostatistics
Sent: Monday, August 06, 2012 2:08 PM
To: 'r-help@r-project.org'
Subject: [R] Force evaluation of a symbol when a function is created
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't arguments
are
evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can easily
simulate the
Matlab behavior. I know that I can live without this in ordinary programming
but it would
make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
__
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.
__
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] Force evaluation of a symbol when a function is created
Thanks to both: Cute question, clever, informative answer.
However, Bill, I don't think you **quite** answered him, although the
modification needed is completely trivial. Of course, I could never
have figured it out without your response.
Anyway, I interpret the question as asking for the function definition
to _implicitly_ pick up the value of Y at the time the function is
defined, rather than explicitly assigning it in local(). The following
are two essentially identical approaches: I prefer the second, because
it's more transparent to me, but that's just a matter of taste.
Y - 3
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
Yielding:
Y - 3
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
F(5)
[1] 15
G(5)
[1] 15
Y - 2
F(5)
[1] 15
G(5)
[1] 15
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
F(5)
[1] 10
G(5)
[1] 10
Cheers,
Bert
On Mon, Aug 6, 2012 at 2:24 PM, William Dunlap wdun...@tibco.com wrote:
You could use local(), as in
F - local({
+Y - 3
+function(x) x * Y
+})
F(7)
[1] 21
Y - 19
F(5)
[1] 15
Look into 'environments' for more.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf
Of Schoenfeld, David Alan,Ph.D.,Biostatistics
Sent: Monday, August 06, 2012 2:08 PM
To: 'r-help@r-project.org'
Subject: [R] Force evaluation of a symbol when a function is created
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't arguments
are
evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can easily
simulate the
Matlab behavior. I know that I can live without this in ordinary
programming but it would
make my port much easier.
Thanks.
The information in this e-mail is intended only for t...{{dropped:26}}
__
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] Force evaluation of a symbol when a function is created
Both of those approaches require the function to be created
at the same time that the environment containing some of its
bindings is created. You can also take an existing function and
assign a new environment to it. E.g.,
f - function(x) y * x
ys - c(2,3,5,7,11)
fs - lapply(ys, function(y) {
env - new.env(parent=baseenv());
env[[y]] - y ;
environment(f) - env ; f })
# fs is a list of functions, all identical except for their environments,
which contain 'y'.
fs[[2]]
function (x)
y * x
environment: 0x05df1c38
fs[[2]](10)
[1] 30
fs[[3]]
function (x)
y * x
environment: 0x05def8c0
fs[[3]](10)
[1] 50
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-Original Message-
From: Bert Gunter [mailto:gunter.ber...@gene.com]
Sent: Monday, August 06, 2012 3:03 PM
To: William Dunlap
Cc: Schoenfeld, David Alan,Ph.D.,Biostatistics; r-help@r-project.org
Subject: Re: [R] Force evaluation of a symbol when a function is created
Thanks to both: Cute question, clever, informative answer.
However, Bill, I don't think you **quite** answered him, although the
modification needed is completely trivial. Of course, I could never
have figured it out without your response.
Anyway, I interpret the question as asking for the function definition
to _implicitly_ pick up the value of Y at the time the function is
defined, rather than explicitly assigning it in local(). The following
are two essentially identical approaches: I prefer the second, because
it's more transparent to me, but that's just a matter of taste.
Y - 3
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
Yielding:
Y - 3
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
F(5)
[1] 15
G(5)
[1] 15
Y - 2
F(5)
[1] 15
G(5)
[1] 15
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
F(5)
[1] 10
G(5)
[1] 10
Cheers,
Bert
On Mon, Aug 6, 2012 at 2:24 PM, William Dunlap wdun...@tibco.com wrote:
You could use local(), as in
F - local({
+Y - 3
+function(x) x * Y
+})
F(7)
[1] 21
Y - 19
F(5)
[1] 15
Look into 'environments' for more.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf
Of Schoenfeld, David Alan,Ph.D.,Biostatistics
Sent: Monday, August 06, 2012 2:08 PM
To: 'r-help@r-project.org'
Subject: [R] Force evaluation of a symbol when a function is created
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't
arguments are
evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can
easily simulate
the
Matlab behavior. I know that I can live without this in ordinary
programming but it
would
make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
__
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.
__
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.
--
Bert Gunter
Genentech Nonclinical Biostatistics
Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-
biostatistics/pdb-ncb-home.htm
__
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] Force evaluation of a symbol when a function is created
Thank you both, this was very helpful. I need to study environments more. Do
either of you know a good source?
-Original Message-
From: Bert Gunter [mailto:gunter.ber...@gene.com]
Sent: Monday, August 06, 2012 6:03 PM
To: William Dunlap
Cc: Schoenfeld, David Alan,Ph.D.,Biostatistics; r-help@r-project.org
Subject: Re: [R] Force evaluation of a symbol when a function is created
Thanks to both: Cute question, clever, informative answer.
However, Bill, I don't think you **quite** answered him, although the
modification needed is completely trivial. Of course, I could never
have figured it out without your response.
Anyway, I interpret the question as asking for the function definition
to _implicitly_ pick up the value of Y at the time the function is
defined, rather than explicitly assigning it in local(). The following
are two essentially identical approaches: I prefer the second, because
it's more transparent to me, but that's just a matter of taste.
Y - 3
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
Yielding:
Y - 3
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
F(5)
[1] 15
G(5)
[1] 15
Y - 2
F(5)
[1] 15
G(5)
[1] 15
F -local({y - Y;function(x)x*y})
G - evalq(function(x)x*y,env=list(y=Y))
F(5)
[1] 10
G(5)
[1] 10
Cheers,
Bert
On Mon, Aug 6, 2012 at 2:24 PM, William Dunlap wdun...@tibco.com wrote:
You could use local(), as in
F - local({
+Y - 3
+function(x) x * Y
+})
F(7)
[1] 21
Y - 19
F(5)
[1] 15
Look into 'environments' for more.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf
Of Schoenfeld, David Alan,Ph.D.,Biostatistics
Sent: Monday, August 06, 2012 2:08 PM
To: 'r-help@r-project.org'
Subject: [R] Force evaluation of a symbol when a function is created
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't arguments
are
evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can easily
simulate the
Matlab behavior. I know that I can live without this in ordinary
programming but it would
make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
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Genentech Nonclinical Biostatistics
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Re: [R] Force evaluation of a symbol when a function is created
On Mon, Aug 6, 2012 at 9:03 PM, Schoenfeld, David Alan,Ph.D.,Biostatistics dschoenf...@partners.org wrote: Thank you both, this was very helpful. I need to study environments more. Do either of you know a good source? Disclaimer: I really have no idea what I'm talking about. They are a somewhat subtle, but exceptionally powerful concept: see, inter alia, cran.r-project.org/doc/contrib/Fox-Companion/appendix-scope.pdf http://www.lemnica.com/esotericR/Introducing-Closures/ If you know a little bit of C, it will go a long way in understanding environments in R. You'll want to (eventually) start to associate R names with C pointers and environments with symbol tables (hence the fact the printed environment is just a memory address) , but that's perhaps a little bit down the road. Environments are different in their fundamental behavior because of this though: they're the best way to get pass by reference in R. Best, Michael __ 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] Force evaluation of a symbol when a function is created
Hi,
Try this:
F-function(x,type=local){Y=3
x*Y}
F(3)
#[1] 9
Y-4
F(3)
#[1] 9
Y-5
F(3)
#[1] 9
A.K.
- Original Message -
From: Schoenfeld, David Alan,Ph.D.,Biostatistics dschoenf...@partners.org
To: 'r-help@r-project.org' r-help@r-project.org
Cc:
Sent: Monday, August 6, 2012 5:07 PM
Subject: [R] Force evaluation of a symbol when a function is created
I am porting a program in matlab to R,
The problem is that Matlab has a feature where symbols that aren't arguments
are evaluated immediately.
That is:
Y=3
F=@(x) x*Y
Will yield a function such that F(2)=6.
If later say. Y=4 then F(2) will still equal 6.
R on the other hand has lazy evaluation.
F-function(x){x*Y}
Will do the following
Y=3
F(2)=6
Y=4
F(2)=8.
Does anyone know of away to defeat lazy evaluation in R so that I can easily
simulate the Matlab behavior. I know that I can live without this in ordinary
programming but it would make my port much easier.
Thanks.
The information in this e-mail is intended only for the ...{{dropped:14}}
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
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