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ravi

2019-Aug-10 20:14 UTC

[R] vectorizing the integrate function

Bert,Thanks a lot for your help. I have a few follow-up questions (shown in the
comment lines).? Numerical values and error for a (i) vector and (ii) array.

a <- seq(from=0,to=1,by=0.5)
b <- seq(from=5,to=10,by=1)
m <- seq(from=10,to=20,by=5)

f2 <-
function(a,b,m)integrate(function(x){exp(-a*x^3-b*x^2-m*x)},lower=0,upper = Inf)
fv <-
Vectorize(f2,vectorize.args=c("a","b","m"),SIMPLIFY=TRUE)

r1 <- fv(a,b,m)
# How to get just the numerical results as an array
# for scalar values of a,b and m, I can get it with 

#s <- integrate(f,0,Inf)$value
# How do I get this for a vector

# Finally, if I want an array for all the values of a, b and m, how should I
proceed?
r <- array(0,c(3,6,3))
r.error <- array(0,c(3,6,3))
# I want the results of the vectorized integrate function in the above arrays.
How do I extract these values?

Thanks,Ravi


    On Saturday, 10 August 2019, 20:03:22 CEST, Bert Gunter <bgunter.4567 at
gmail.com> wrote:
 
 Ravi:
First of all, you're calling Vectorize incorrectly. The first argument must
be a function *name*, not a function call. Here's what you need to do (and
thanks for the reprex -- wouldn't have been able to help without it!):
f2 <- function(a,b,c)integrate(function(x){exp(-a*x^3-b*x^2-c*x)},lower
=0,upper = Inf)
fv <-
Vectorize(f2,vectorize.args=c("a","b","c"),SIMPLIFY=TRUE)
Second of all, as you may realize, the vectorization uses mapply() and so
vectorizes the c(a,b,c) triplet "in parallel," which will
"recycle" shorter arguments to the length of longer. Hence you will
get 6 results from your example:> fv(a,b,m)? ? ? ? ? ? ?[,1] ? ? ? ? [,2] ? ? ? ? [,3] ? ? ? ?[,4] ? ? ? ? [,5] ? ? ? ?
[,6] ? ? ? ?
value ? ? ? ?0.09207851 ? 0.0635289 ? ?0.04837997 ?0.08856628 ? 0.06224138 ?
0.04777941 ?
abs.error ? ?3.365173e-08 3.108388e-06 1.00652e-09 3.284876e-09 1.796619e-08
6.348142e-09
subdivisions 2 ? ? ? ? ? ?1 ? ? ? ? ? ?2 ? ? ? ? ? 2 ? ? ? ? ? ?2 ? ? ? ? ? ?2 ?
? ? ? ?
message ? ? ?"OK" ? ? ? ? "OK" ? ? ? ? "OK" ? ? ?
?"OK" ? ? ? ? "OK" ? ? ? ? "OK" ? ? ? ?
call ? ? ? ? Expression ? Expression ? Expression ?Expression ? Expression ?
Expression?

Cheers,Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sat, Aug 10, 2019 at 10:20 AM ravi via R-help <r-help at r-project.org>
wrote:

Hi all,I am having some difficulties in vectorizing the integrate function. Let
me explain with an example.
a <- 10; b <- 3; c <- 4
f <- function(x) {exp(-a*x^3-b*x^2-c*x)}
integrate(f,0,Inf) # works fine

My difficulties start when I want to vectorize.

# attempts to vectorize fail
a <- seq(from=0,to=1,by=0.5)
b <- seq(from=5,to=10,by=1)
m <- seq(from=10,to=20,by=5)
f2 <- function(x,a,b,c) {exp(-a*x^3-b*x^2-m*x)}
fv <-
Vectorize(integrate(f2,0,Inf),vectorize.args=c("a","b","m"),SIMPLIFY=TRUE)

I want the result as a 3-d array with dimensions of the lengths of a, b and c. I
have tried several variants but am not having much luck. Will appreciate any
help that I can get.
Thanks,Ravi Sutradhara




? ? ? ? [[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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]]

Rui Barradas

2019-Aug-10 22:03 UTC

head link

[R] vectorizing the integrate function

Hello,

The following code might not be the best way of computing the integrals 
for all combinations of the arguments but it gets the job done and I 
believe it's readable code.


f2 <- function(a, b, c){
   integrate(function(x) {exp(-a*x^3 - b*x^2 - c*x)},
             lower = 0, upper = Inf)
}

f2_all_args <- function(a, b, c){
   lapply(a, function(.a)
     lapply(b, function(.b)
       lapply(c, function(.c)
         f2(.a, .b, .c)[1:2]
       )
     )
   )
}

a <- seq(from = 0, to = 1, by = 0.5)
b <- seq(from = 5, to = 10, by = 1)
m <- seq(from = 10, to = 20, by = 5)

res <- f2_all_args(a, b, m)

r <- array(0, c(3, 6, 3))
r.error <- array(0, c(3, 6, 3))

for(i in seq_along(a)){
   res_i <- res[[i]]
   for(j in seq_along(b)){
     res_i_j <- res_i[[j]]
     for(k in seq_along(m)){
       r[i, j, k] <- res_i_j[[k]]$value
       r.error[i, j, k] <- res_i_j[[k]]$abs.error
     }
   }
}


Hope this helps,

Rui Barradas


?s 21:14 de 10/08/19, ravi via R-help escreveu:>   Bert,Thanks a lot for your help. I have a few follow-up questions (shown
in the comment lines).? Numerical values and error for a (i) vector and (ii)
array.
> 
> a <- seq(from=0,to=1,by=0.5)
> b <- seq(from=5,to=10,by=1)
> m <- seq(from=10,to=20,by=5)
> 
> f2 <-
function(a,b,m)integrate(function(x){exp(-a*x^3-b*x^2-m*x)},lower=0,upper = Inf)
> fv <-
Vectorize(f2,vectorize.args=c("a","b","m"),SIMPLIFY=TRUE)
> 
> r1 <- fv(a,b,m)
> # How to get just the numerical results as an array
> # for scalar values of a,b and m, I can get it with
> 
> #s <- integrate(f,0,Inf)$value
> # How do I get this for a vector
> 
> # Finally, if I want an array for all the values of a, b and m, how should
I proceed?
> r <- array(0,c(3,6,3))
> r.error <- array(0,c(3,6,3))
> # I want the results of the vectorized integrate function in the above
arrays. How do I extract these values?
> 
> Thanks,Ravi
> 
> 
>      On Saturday, 10 August 2019, 20:03:22 CEST, Bert Gunter
<bgunter.4567 at gmail.com> wrote:
>   
>   Ravi:
> First of all, you're calling Vectorize incorrectly. The first argument
must be a function *name*, not a function call. Here's what you need to do
(and thanks for the reprex -- wouldn't have been able to help without it!):
> f2 <- function(a,b,c)integrate(function(x){exp(-a*x^3-b*x^2-c*x)},lower
=0,upper = Inf)
> fv <-
Vectorize(f2,vectorize.args=c("a","b","c"),SIMPLIFY=TRUE)
> Second of all, as you may realize, the vectorization uses mapply() and so
vectorizes the c(a,b,c) triplet "in parallel," which will
"recycle" shorter arguments to the length of longer. Hence you will
get 6 results from your example:
>> fv(a,b,m)
>  ? ? ? ? ? ? ?[,1] ? ? ? ? [,2] ? ? ? ? [,3] ? ? ? ?[,4] ? ? ? ? [,5] ? ? ?
? [,6]
> value ? ? ? ?0.09207851 ? 0.0635289 ? ?0.04837997 ?0.08856628 ? 0.06224138
? 0.04777941
> abs.error ? ?3.365173e-08 3.108388e-06 1.00652e-09 3.284876e-09
1.796619e-08 6.348142e-09
> subdivisions 2 ? ? ? ? ? ?1 ? ? ? ? ? ?2 ? ? ? ? ? 2 ? ? ? ? ? ?2 ? ? ? ? ?
?2
> message ? ? ?"OK" ? ? ? ? "OK" ? ? ? ? "OK" ?
? ? ?"OK" ? ? ? ? "OK" ? ? ? ? "OK"
> call ? ? ? ? Expression ? Expression ? Expression ?Expression ? Expression
? Expression
> 
> Cheers,Bert
> Bert Gunter
> 
> "The trouble with having an open mind is that people keep coming along
and sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip
)
> 
> 
> On Sat, Aug 10, 2019 at 10:20 AM ravi via R-help <r-help at
r-project.org> wrote:
> 
> Hi all,I am having some difficulties in vectorizing the integrate function.
Let me explain with an example.
> a <- 10; b <- 3; c <- 4
> f <- function(x) {exp(-a*x^3-b*x^2-c*x)}
> integrate(f,0,Inf) # works fine
> 
> My difficulties start when I want to vectorize.
> 
> # attempts to vectorize fail
> a <- seq(from=0,to=1,by=0.5)
> b <- seq(from=5,to=10,by=1)
> m <- seq(from=10,to=20,by=5)
> f2 <- function(x,a,b,c) {exp(-a*x^3-b*x^2-m*x)}
> fv <-
Vectorize(integrate(f2,0,Inf),vectorize.args=c("a","b","m"),SIMPLIFY=TRUE)
> 
> I want the result as a 3-d array with dimensions of the lengths of a, b and
c. I have tried several variants but am not having much luck. Will appreciate
any help that I can get.
> Thanks,Ravi Sutradhara
> 
> 
> 
> 
>  ? ? ? ? [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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]]
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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

2019-Aug-10 22:51 UTC

head link

[R] vectorizing the integrate function

Cleaner, I think, is to use ?expand.grid and ?do.call, noting that any
n-column data frame is also an n-component list.

Using your example as before:
> f2 <- function(a,b,m)integrate(function(x){exp(-a*x^3-b*x^2-m*x)},lower
=0,upper = Inf)> fv <-
Vectorize(f2,vectorize.args=c("a","b","m"),SIMPLIFY=TRUE)
## Now use expand.grid to get all combinations of a,b, and m in a data frame
> allvals <- expand.grid(a=a, b=b, m=m)## Here's what it looks like (note the **named** columns to avoid
problems)> head(allvals)    a b  m
1 0.0 5 10
2 0.5 5 10
3 1.0 5 10
4 0.0 6 10
5 0.5 6 10
6 1.0 6 10
## etc.  3 x 6 x 3 = 54 rows in all

## now use do.call to do fv() on these three column vectors (considered as
a list of 3 components)
> results <- do.call(fv, allvals)
## So what does results look like?> class(results)
[1] "matrix"> dim(results)
[1]  5 54> dimnames(results)[[1]][1] "value"        "abs.error"    "subdivisions"
"message"      "call"

## So the first row of the matrix contains the values. If you extract them
by results[1, ],
## you'll find, however, that it's a list of 54 components, each of
which
is a vector with
## one value. So unlist it first to avoid this:
> vals <- unlist(results[1,])
> vals [1] 0.09207851 0.09193111 0.09178672 0.09083412 0.09070066 0.09056960
0.08966646 0.08954474
 [9] 0.08942499 0.08856628 0.08845459 0.08834454 0.08752598 0.08742295
0.08732131 0.08653926
[17] 0.08644379 0.08634949 0.06403081 0.06398995 0.06394947 0.06356740
0.06352890 0.06349075
[25] 0.06312099 0.06308463 0.06304856 0.06269028 0.06265583 0.06262164
0.06227409 0.06224138
[33] 0.06220891 0.06187141 0.06184029 0.06180937 0.04883372 0.04881874
0.04880384 0.04861813
[41] 0.04860372 0.04858939 0.04840766 0.04839378 0.04837997 0.04820203
0.04818865 0.04817532
[49] 0.04800099 0.04798808 0.04797521 0.04780433 0.04779185 0.04777941

You can either convert this into an array or just add it as a column to
allvals. The results are listed in
the order given there.

Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sat, Aug 10, 2019 at 3:03 PM Rui Barradas <ruipbarradas at sapo.pt>
wrote:
> Hello,
>
> The following code might not be the best way of computing the integrals
> for all combinations of the arguments but it gets the job done and I
> believe it's readable code.
>
>
> f2 <- function(a, b, c){
>    integrate(function(x) {exp(-a*x^3 - b*x^2 - c*x)},
>              lower = 0, upper = Inf)
> }
>
> f2_all_args <- function(a, b, c){
>    lapply(a, function(.a)
>      lapply(b, function(.b)
>        lapply(c, function(.c)
>          f2(.a, .b, .c)[1:2]
>        )
>      )
>    )
> }
>
> a <- seq(from = 0, to = 1, by = 0.5)
> b <- seq(from = 5, to = 10, by = 1)
> m <- seq(from = 10, to = 20, by = 5)
>
> res <- f2_all_args(a, b, m)
>
> r <- array(0, c(3, 6, 3))
> r.error <- array(0, c(3, 6, 3))
>
> for(i in seq_along(a)){
>    res_i <- res[[i]]
>    for(j in seq_along(b)){
>      res_i_j <- res_i[[j]]
>      for(k in seq_along(m)){
>        r[i, j, k] <- res_i_j[[k]]$value
>        r.error[i, j, k] <- res_i_j[[k]]$abs.error
>      }
>    }
> }
>
>
> Hope this helps,
>
> Rui Barradas
>
>
> ?s 21:14 de 10/08/19, ravi via R-help escreveu:
> >   Bert,Thanks a lot for your help. I have a few follow-up questions
> (shown in the comment lines).  Numerical values and error for a (i) vector
> and (ii) array.
> >
> > a <- seq(from=0,to=1,by=0.5)
> > b <- seq(from=5,to=10,by=1)
> > m <- seq(from=10,to=20,by=5)
> >
> > f2 <-
> function(a,b,m)integrate(function(x){exp(-a*x^3-b*x^2-m*x)},lower=0,upper
> Inf)
> > fv <-
Vectorize(f2,vectorize.args=c("a","b","m"),SIMPLIFY=TRUE)
> >
> > r1 <- fv(a,b,m)
> > # How to get just the numerical results as an array
> > # for scalar values of a,b and m, I can get it with
> >
> > #s <- integrate(f,0,Inf)$value
> > # How do I get this for a vector
> >
> > # Finally, if I want an array for all the values of a, b and m, how
> should I proceed?
> > r <- array(0,c(3,6,3))
> > r.error <- array(0,c(3,6,3))
> > # I want the results of the vectorized integrate function in the above
> arrays. How do I extract these values?
> >
> > Thanks,Ravi
> >
> >
> >      On Saturday, 10 August 2019, 20:03:22 CEST, Bert Gunter <
> bgunter.4567 at gmail.com> wrote:
> >
> >   Ravi:
> > First of all, you're calling Vectorize incorrectly. The first
argument
> must be a function *name*, not a function call. Here's what you need to
do
> (and thanks for the reprex -- wouldn't have been able to help without
it!):
> > f2 <-
function(a,b,c)integrate(function(x){exp(-a*x^3-b*x^2-c*x)},lower
> =0,upper = Inf)
> > fv <-
Vectorize(f2,vectorize.args=c("a","b","c"),SIMPLIFY=TRUE)
> > Second of all, as you may realize, the vectorization uses mapply() and
> so vectorizes the c(a,b,c) triplet "in parallel," which will
"recycle"
> shorter arguments to the length of longer. Hence you will get 6 results
> from your example:
> >> fv(a,b,m)
> >               [,1]         [,2]         [,3]        [,4]         [,5]
>       [,6]
> > value        0.09207851   0.0635289    0.04837997  0.08856628
> 0.06224138   0.04777941
> > abs.error    3.365173e-08 3.108388e-06 1.00652e-09 3.284876e-09
> 1.796619e-08 6.348142e-09
> > subdivisions 2            1            2           2            2
>      2
> > message      "OK"         "OK"        
"OK"        "OK"         "OK"
>     "OK"
> > call         Expression   Expression   Expression  Expression
> Expression   Expression
> >
> > Cheers,Bert
> > Bert Gunter
> >
> > "The trouble with having an open mind is that people keep coming
along
> and sticking things into it."
> > -- Opus (aka Berkeley Breathed in his "Bloom County" comic
strip )
> >
> >
> > On Sat, Aug 10, 2019 at 10:20 AM ravi via R-help <r-help at
r-project.org>
> wrote:
> >
> > Hi all,I am having some difficulties in vectorizing the integrate
> function. Let me explain with an example.
> > a <- 10; b <- 3; c <- 4
> > f <- function(x) {exp(-a*x^3-b*x^2-c*x)}
> > integrate(f,0,Inf) # works fine
> >
> > My difficulties start when I want to vectorize.
> >
> > # attempts to vectorize fail
> > a <- seq(from=0,to=1,by=0.5)
> > b <- seq(from=5,to=10,by=1)
> > m <- seq(from=10,to=20,by=5)
> > f2 <- function(x,a,b,c) {exp(-a*x^3-b*x^2-m*x)}
> > fv <-
>
Vectorize(integrate(f2,0,Inf),vectorize.args=c("a","b","m"),SIMPLIFY=TRUE)
> >
> > I want the result as a 3-d array with dimensions of the lengths of a,
b
> and c. I have tried several variants but am not having much luck. Will
> appreciate any help that I can get.
> > Thanks,Ravi Sutradhara
> >
> >
> >
> >
> >          [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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]]
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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]]

R help - Aug 2019 - vectorizing the integrate function

[R] vectorizing the integrate function

[R] vectorizing the integrate function

[R] vectorizing the integrate function