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Raznahan, Armin (NIH/NIMH) [E]

2010-Oct-05 01:10 UTC

[R] Using as.polynomial() over a matrix

Hello All

First - a warning. I'm not very R or programming savvy. 

I am trying to do something without much luck, and have scoured help-pages, but
nothing has come up. Here it is:

I have a matrix (m) of approx 40,000 rows and 3 columns, filled with numbers.

I would like to convert the contents of this matrix into another matrix (m_p),
where the numbers of (m) have been coerced into a polynomial - using a function
called "as.polynomial()" from the package (polynom). Each row of (m)
contains 3 terms to be made into a polynomial in the equivalent row of (m_p).

I have tried a coupe of things:

------------------------------
1. Using apply()

m_p<-apply(m, 2, as.polynomial)

Here is what happens..
> dim(m)
[1] 40962     3> m_p<-apply(m, 2, as.polynomial)
> m_p[1:5,]            dM_I    dM_a.c dM_a.c.sq
[1,] -0.00593058 -0.000688  3.65e-05
[2,] -0.01913294  0.000103  1.41e-04
[3,] -0.01317958 -0.001190  1.49e-04
[4,] -0.02651112 -0.001550  2.37e-04
[5,] -0.01680289 -0.003520  2.86e-04

So - looks like the coercion hasn't worked. BUT, if I do things piecemeal -
it looks ok..
> m_p1<-as.polynomial(m[1,])
> m_p1-0.00593058 - 0.000688*x + 3.65e-05*x^2 
--------------------------------
-------------------------------
2. This made me think I was making some wrong assumptions using apply(). So I
wrote a function "test()", to take each row of (m) , use
as.polynomial() on it,  and stick the results into a new matrix, which it would
then return..

test<-function(x){
a<-nrow(x)
b<-ncol(x)
c<-matrix(0, a, b)
for (i in 1:a) {
c[i,]<-as.polynomial(x[i,]) }
return (c)
}
> m_p<-test(m)
> dim(m_p)
[1] 40962     3> m_p[1:5,]            [,1]      [,2]     [,3]
[1,] -0.00593058 -0.000688 3.65e-05
[2,] -0.01913294  0.000103 1.41e-04
[3,] -0.01317958 -0.001190 1.49e-04
[4,] -0.02651112 -0.001550 2.37e-04
[5,] -0.01680289 -0.003520 2.86e-04

-------------------

I don't know why I can do what I want when taking each line at a time, but
not when trying to run through the whole matrix.

Sorry if missing something obvious.  Any help/pointers would be very gratefully
received

Thanks v much

Armin

Nikhil Kaza

2010-Oct-05 01:30 UTC

head link

[R] Using as.polynomial() over a matrix

it looks like as. polynomial merely stores the coefficients of the  
polynomial.
	"Internally, polynomials are simply numeric coefficient vectors of  
class "polynomial". "
If you really want to print it in the form you want try this.

m <- matrix(rnorm(3000),1000,3)
apply(m, 1, function(x){print(as.polynomial(x))}) # Not sure why you  
are using 2 i.e. applying the formula column wise instead of 1, row  
wise.


Nikhil Kaza
Asst. Professor,
City and Regional Planning
University of North Carolina

nikhil.list@gmail.com

On Oct 4, 2010, at 9:10 PM, Raznahan, Armin (NIH/NIMH) [E] wrote:
> Hello All
>
> First - a warning. I'm not very R or programming savvy.
>
> I am trying to do something without much luck, and have scoured help- 
> pages, but nothing has come up. Here it is:
>
> I have a matrix (m) of approx 40,000 rows and 3 columns, filled with  
> numbers.
>
> I would like to convert the contents of this matrix into another  
> matrix (m_p), where the numbers of (m) have been coerced into a  
> polynomial - using a function called "as.polynomial()" from the  
> package (polynom). Each row of (m) contains 3 terms to be made into  
> a polynomial in the equivalent row of (m_p).
>
> I have tried a coupe of things:
>
> ------------------------------
> 1. Using apply()
>
> m_p<-apply(m, 2, as.polynomial)
>
> Here is what happens..
>
>> dim(m)
> [1] 40962     3
>> m_p<-apply(m, 2, as.polynomial)
>> m_p[1:5,]
>            dM_I    dM_a.c dM_a.c.sq
> [1,] -0.00593058 -0.000688  3.65e-05
> [2,] -0.01913294  0.000103  1.41e-04
> [3,] -0.01317958 -0.001190  1.49e-04
> [4,] -0.02651112 -0.001550  2.37e-04
> [5,] -0.01680289 -0.003520  2.86e-04
>
> So - looks like the coercion hasn't worked. BUT, if I do things  
> piecemeal - it looks ok..
>
>> m_p1<-as.polynomial(m[1,])
>> m_p1
> -0.00593058 - 0.000688*x + 3.65e-05*x^2
> --------------------------------
> -------------------------------
> 2. This made me think I was making some wrong assumptions using  
> apply(). So I wrote a function "test()", to take each row of (m)
,
> use as.polynomial() on it,  and stick the results into a new matrix,  
> which it would then return..
>
> test<-function(x){
> a<-nrow(x)
> b<-ncol(x)
> c<-matrix(0, a, b)
> for (i in 1:a) {
> c[i,]<-as.polynomial(x[i,]) }
> return (c)
> }
>
>> m_p<-test(m)
>> dim(m_p)
> [1] 40962     3
>> m_p[1:5,]
>            [,1]      [,2]     [,3]
> [1,] -0.00593058 -0.000688 3.65e-05
> [2,] -0.01913294  0.000103 1.41e-04
> [3,] -0.01317958 -0.001190 1.49e-04
> [4,] -0.02651112 -0.001550 2.37e-04
> [5,] -0.01680289 -0.003520 2.86e-04
>
> -------------------
>
> I don't know why I can do what I want when taking each line at a  
> time, but not when trying to run through the whole matrix.
>
> Sorry if missing something obvious.  Any help/pointers would be very  
> gratefully received
>
> Thanks v much
>
> Armin
>
> ______________________________________________
> 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.

	[[alternative HTML version deleted]]

MacQueen, Don

2010-Oct-06 03:22 UTC

head link

[R] Using as.polynomial() over a matrix

The key is in the help page for apply. It says (in part):


    In all cases the result is coerced by ?as.vector? to one of the
     basic vector types before the dimensions are set, so that (for
     example) factor results will be coerced to a character array.

So although as.polynomial() returns an object of class polynomial, apply
then runs as.vector() on it, which makes it not a polynomial class any more.

You should also be running apply in the first index (1) not the second (2),
as in
   apply(  whatever, 1, function )
If you want it to apply the function to each row, which I think you do. The
strange result you get is also explained by the help page:

    If each call to ?FUN? returns a vector of length ?n?, then ?apply?
     returns an array of dimension ?c(n, dim(X)[MARGIN])? if ?n > 1?.
 
This example will get you closer:
> tmp <- matrix(1:12, ncol=3, byrow=TRUE)
> foo <- apply(tmp,1, list)
> lapply(foo,function(x) as.polynomial(unlist(x)))[[1]]
1 + 2*x + 3*x^2 

[[2]]
4 + 5*x + 6*x^2 

[[3]]
7 + 8*x + 9*x^2 

[[4]]
10 + 11*x + 12*x^2 

-Don


On 10/4/10 6:10 PM, "Raznahan, Armin (NIH/NIMH) [E]"
<raznahana at mail.nih.gov> wrote:
> Hello All
> 
> First - a warning. I'm not very R or programming savvy.
> 
> I am trying to do something without much luck, and have scoured help-pages,
> but nothing has come up. Here it is:
> 
> I have a matrix (m) of approx 40,000 rows and 3 columns, filled with
numbers.
> 
> I would like to convert the contents of this matrix into another matrix
(m_p),
> where the numbers of (m) have been coerced into a polynomial - using a
> function called "as.polynomial()" from the package (polynom).
Each row of (m)
> contains 3 terms to be made into a polynomial in the equivalent row of
(m_p).
> 
> I have tried a coupe of things:
> 
> ------------------------------
> 1. Using apply()
> 
> m_p<-apply(m, 2, as.polynomial)
> 
> Here is what happens..
> 
>> dim(m)
> [1] 40962     3
>> m_p<-apply(m, 2, as.polynomial)
>> m_p[1:5,]
>             dM_I    dM_a.c dM_a.c.sq
> [1,] -0.00593058 -0.000688  3.65e-05
> [2,] -0.01913294  0.000103  1.41e-04
> [3,] -0.01317958 -0.001190  1.49e-04
> [4,] -0.02651112 -0.001550  2.37e-04
> [5,] -0.01680289 -0.003520  2.86e-04
> 
> So - looks like the coercion hasn't worked. BUT, if I do things
piecemeal - it
> looks ok..
> 
>> m_p1<-as.polynomial(m[1,])
>> m_p1
> -0.00593058 - 0.000688*x + 3.65e-05*x^2
> --------------------------------
> -------------------------------
> 2. This made me think I was making some wrong assumptions using apply(). So
I
> wrote a function "test()", to take each row of (m) , use
as.polynomial() on
> it,  and stick the results into a new matrix, which it would then return..
> 
> test<-function(x){
> a<-nrow(x)
> b<-ncol(x)
> c<-matrix(0, a, b)
> for (i in 1:a) {
> c[i,]<-as.polynomial(x[i,]) }
> return (c)
> }
> 
>> m_p<-test(m)
>> dim(m_p)
> [1] 40962     3
>> m_p[1:5,]
>             [,1]      [,2]     [,3]
> [1,] -0.00593058 -0.000688 3.65e-05
> [2,] -0.01913294  0.000103 1.41e-04
> [3,] -0.01317958 -0.001190 1.49e-04
> [4,] -0.02651112 -0.001550 2.37e-04
> [5,] -0.01680289 -0.003520 2.86e-04
> 
> -------------------
> 
> I don't know why I can do what I want when taking each line at a time,
but not
> when trying to run through the whole matrix.
> 
> Sorry if missing something obvious.  Any help/pointers would be very
> gratefully received
> 
> Thanks v much
> 
> Armin
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://BLOCKEDstat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://BLOCKEDwww.BLOCKEDR-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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