Re: [Rd] outer not applying a constant function

[Martin Maechler]

> William Dunlap 
> on Mon, 20 Mar 2017 10:20:11 -0700 writes:

>> Or is this a bad idea?
> I don't like the proposal.  I have seen code like the following (in
> fact, I have written such code, where I had forgotten a function was
> not vectorized) where the error would have been discovered much later
> if outer() didn't catch it.

>> outer(1:3, 11:13, sum)
>  Error in outer(1:3, 11:13, sum) :
>dims [product 9] do not match the length of object [1]

> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com

You are right, thank you!
Such a "convenience change" would not be a good idea.

Martin Maechler
ETH Zurich




> On Mon, Mar 20, 2017 at 6:36 AM, Martin Maechler
>  wrote:
>>> Gebhardt, Albrecht 
>>> on Sun, 19 Mar 2017 09:14:56 + writes:
>> 
>> > Hi,
>> > the function outer can not apply a constant function as in the last 
line of the following example:
>> 
>> >> xg <- 1:4
>> >> yg <- 1:4
>> >> fxyg <- outer(xg, yg, function(x,y) x*y)
>> >> fconstg <- outer(xg, yg, function(x,y) 1.0)
>> > Error in outer(xg, yg, function(x, y) 1) :
>> > dims [product 16] do not match the length of object [1]
>> 
>> > Of course there are simpler ways to construct a constant matrix, that 
is not my point.
>> 
>> > It happens for me in the context of generating matrices of partial 
derivatives, and if on of these partial derivatives happens to be constant it 
fails.
>> 
>> > So e.g this works:
>> 
>> > library(Deriv)
>> > f <- function(x,y) (x-1.5)*(y-1)*(x-1.8)+(y-1.9)^2*(x-1.1)^3
>> > fx <- Deriv(f,"x")
>> > fy <- Deriv(f,"y")
>> > fxy <- Deriv(Deriv(f,"y"),"x")
>> > fxx <- Deriv(Deriv(f,"x"),"x")
>> > fyy <- Deriv(Deriv(f,"y"),"y")
>> 
>> > fg   <- outer(xg,yg,f)
>> > fxg  <- outer(xg,yg,fx)
>> > fyg  <- outer(xg,yg,fy)
>> > fxyg <- outer(xg,yg,fxy)
>> > fxxg <- outer(xg,yg,fxx)
>> > fyyg <- outer(xg,yg,fyy)
>> 
>> > And with
>> 
>> > f <- function(x,y) x+y
>> 
>> > it stops working. Of course I can manually fix this for that special 
case, but thats not my point. I simply thought "outer" should be able to handle 
constant functions.
>> 
>> ?outer   clearly states that  FUN  needs to be vectorized
>> 
>> but  function(x,y) 1is not.
>> 
>> It is easy to solve by wrapping the function in Vectorize(.):
>> 
>>> x <- 1:3; y <- 1:4
>> 
>>> outer(x,y, function(x,y) 1)
>> Error in dim(robj) <- c(dX, dY) :
>> dims [product 12] do not match the length of object [1]
>> 
>>> outer(x,y, Vectorize(function(x,y) 1))
>> [,1] [,2] [,3] [,4]
>> [1,]1111
>> [2,]1111
>> [3,]1111
>> 
>> 
>> 
>> So, your "should"  above must be read in the sense
>> 
>> "It really would be convenient here and
>> correspond to other "recycling" behavior of R"
>> 
>> and I agree with that, having experienced the same inconvenience
>> as you several times in the past.
>> 
>> outer() being a nice R-level function (i.e., no C speed up)
>> makes it easy to improve:
>> 
>> Adding something like the line
>> 
>> if(length(robj) == 1L) robj <- rep.int(robj, dX*dY)
>> 
>> beforedim(robj) <- c(dX, dY)   [which gave the error]
>> 
>> would solve the issue and not cost much (in the cases it is unneeded).
>> 
>> Or is this a bad idea?
>> 
>> __
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>> https://stat.ethz.ch/mailman/listinfo/r-devel

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Re: [Rd] outer not applying a constant function

[William Dunlap via R-devel]

> Or is this a bad idea?

I don't like the proposal.  I have seen code like the following (in
fact, I have written such code, where I had forgotten a function was
not vectorized) where the error would have been discovered much later
if outer() didn't catch it.

  > outer(1:3, 11:13, sum)
  Error in outer(1:3, 11:13, sum) :
dims [product 9] do not match the length of object [1]

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Mon, Mar 20, 2017 at 6:36 AM, Martin Maechler
 wrote:
>> Gebhardt, Albrecht 
>> on Sun, 19 Mar 2017 09:14:56 + writes:
>
> > Hi,
> > the function outer can not apply a constant function as in the last 
> line of the following example:
>
> >> xg <- 1:4
> >> yg <- 1:4
> >> fxyg <- outer(xg, yg, function(x,y) x*y)
> >> fconstg <- outer(xg, yg, function(x,y) 1.0)
> > Error in outer(xg, yg, function(x, y) 1) :
> > dims [product 16] do not match the length of object [1]
>
> > Of course there are simpler ways to construct a constant matrix, that 
> is not my point.
>
> > It happens for me in the context of generating matrices of partial 
> derivatives, and if on of these partial derivatives happens to be constant it 
> fails.
>
> > So e.g this works:
>
> > library(Deriv)
> > f <- function(x,y) (x-1.5)*(y-1)*(x-1.8)+(y-1.9)^2*(x-1.1)^3
> > fx <- Deriv(f,"x")
> > fy <- Deriv(f,"y")
> > fxy <- Deriv(Deriv(f,"y"),"x")
> > fxx <- Deriv(Deriv(f,"x"),"x")
> > fyy <- Deriv(Deriv(f,"y"),"y")
>
> > fg   <- outer(xg,yg,f)
> > fxg  <- outer(xg,yg,fx)
> > fyg  <- outer(xg,yg,fy)
> > fxyg <- outer(xg,yg,fxy)
> > fxxg <- outer(xg,yg,fxx)
> > fyyg <- outer(xg,yg,fyy)
>
> > And with
>
> > f <- function(x,y) x+y
>
> > it stops working. Of course I can manually fix this for that special 
> case, but thats not my point. I simply thought "outer" should be able to 
> handle constant functions.
>
> ?outer   clearly states that  FUN  needs to be vectorized
>
> but  function(x,y) 1is not.
>
> It is easy to solve by wrapping the function in Vectorize(.):
>
>> x <- 1:3; y <- 1:4
>
>> outer(x,y, function(x,y) 1)
> Error in dim(robj) <- c(dX, dY) :
>   dims [product 12] do not match the length of object [1]
>
>> outer(x,y, Vectorize(function(x,y) 1))
>  [,1] [,2] [,3] [,4]
> [1,]1111
> [2,]1111
> [3,]1111
>
> 
>
> So, your "should"  above must be read in the sense
>
>   "It really would be convenient here and
>correspond to other "recycling" behavior of R"
>
> and I agree with that, having experienced the same inconvenience
> as you several times in the past.
>
> outer() being a nice R-level function (i.e., no C speed up)
> makes it easy to improve:
>
> Adding something like the line
>
> if(length(robj) == 1L) robj <- rep.int(robj, dX*dY)
>
> beforedim(robj) <- c(dX, dY)   [which gave the error]
>
> would solve the issue and not cost much (in the cases it is unneeded).
>
> Or is this a bad idea?
>
> __
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

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Re: [Rd] outer not applying a constant function

[Martin Maechler]

> Gebhardt, Albrecht 
> on Sun, 19 Mar 2017 09:14:56 + writes:

> Hi,
> the function outer can not apply a constant function as in the last line 
of the following example:

>> xg <- 1:4
>> yg <- 1:4
>> fxyg <- outer(xg, yg, function(x,y) x*y)
>> fconstg <- outer(xg, yg, function(x,y) 1.0)
> Error in outer(xg, yg, function(x, y) 1) :
> dims [product 16] do not match the length of object [1]

> Of course there are simpler ways to construct a constant matrix, that is 
not my point.

> It happens for me in the context of generating matrices of partial 
derivatives, and if on of these partial derivatives happens to be constant it 
fails.

> So e.g this works:

> library(Deriv)
> f <- function(x,y) (x-1.5)*(y-1)*(x-1.8)+(y-1.9)^2*(x-1.1)^3
> fx <- Deriv(f,"x")
> fy <- Deriv(f,"y")
> fxy <- Deriv(Deriv(f,"y"),"x")
> fxx <- Deriv(Deriv(f,"x"),"x")
> fyy <- Deriv(Deriv(f,"y"),"y")

> fg   <- outer(xg,yg,f)
> fxg  <- outer(xg,yg,fx)
> fyg  <- outer(xg,yg,fy)
> fxyg <- outer(xg,yg,fxy)
> fxxg <- outer(xg,yg,fxx)
> fyyg <- outer(xg,yg,fyy)

> And with

> f <- function(x,y) x+y

> it stops working. Of course I can manually fix this for that special 
case, but thats not my point. I simply thought "outer" should be able to handle 
constant functions.

?outer   clearly states that  FUN  needs to be vectorized

but  function(x,y) 1is not.

It is easy to solve by wrapping the function in Vectorize(.):

> x <- 1:3; y <- 1:4

> outer(x,y, function(x,y) 1)
Error in dim(robj) <- c(dX, dY) : 
  dims [product 12] do not match the length of object [1]

> outer(x,y, Vectorize(function(x,y) 1))
 [,1] [,2] [,3] [,4]
[1,]1111
[2,]1111
[3,]1111



So, your "should"  above must be read in the sense

  "It really would be convenient here and
   correspond to other "recycling" behavior of R"

and I agree with that, having experienced the same inconvenience
as you several times in the past.

outer() being a nice R-level function (i.e., no C speed up)
makes it easy to improve:

Adding something like the line

if(length(robj) == 1L) robj <- rep.int(robj, dX*dY)

beforedim(robj) <- c(dX, dY)   [which gave the error]

would solve the issue and not cost much (in the cases it is unneeded).

Or is this a bad idea?

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[Rd] outer not applying a constant function

[Gebhardt, Albrecht]

Hi,

the function outer can not apply a constant function as in the last line of the 
following example:

> xg <- 1:4
> yg <- 1:4
> fxyg <- outer(xg, yg, function(x,y) x*y)
> fconstg <- outer(xg, yg, function(x,y) 1.0)
Error in outer(xg, yg, function(x, y) 1) :
  dims [product 16] do not match the length of object [1]

Of course there are simpler ways to construct a constant matrix, that is not my 
point.

It happens for me in the context of generating matrices of partial derivatives, 
and if on of these partial derivatives happens to be constant it fails.

So e.g this works:

library(Deriv)
f <- function(x,y) (x-1.5)*(y-1)*(x-1.8)+(y-1.9)^2*(x-1.1)^3
fx <- Deriv(f,"x")
fy <- Deriv(f,"y")
fxy <- Deriv(Deriv(f,"y"),"x")
fxx <- Deriv(Deriv(f,"x"),"x")
fyy <- Deriv(Deriv(f,"y"),"y")

fg   <- outer(xg,yg,f)
fxg  <- outer(xg,yg,fx)
fyg  <- outer(xg,yg,fy)
fxyg <- outer(xg,yg,fxy)
fxxg <- outer(xg,yg,fxx)
fyyg <- outer(xg,yg,fyy)

And with

f <- function(x,y) x+y

it stops working. Of course I can manually fix this for that special case, but 
thats not my point. I simply thought "outer" should be able to handle constant 
functions.

Best regards

Albrecht




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