Well, sort of...
aggregate() is basically a wrapper for lapply(), which ultimately must loop
over the function call at the R interpreter level, as opposed to vectorized
functions that loop at the C level and hence can be orders of magnitude
faster. As a result, there is often little difference in
You don't need loops at all.
grw <- aggregate(gw ~ ts + ISEG + iter, data = dat, FUN = sum)
GRW <- aggregate(gw ~ ts + ISEG, data = grw, FUN = function(x){max(x) -
min(x)})
DC <- aggregate(div ~ ts + ISEG, data = subset(dat, IRCH == 1), FUN =
function(x){max(x) - min(x)})
iter <- a
You are certainly in Circle 2 of 'The R Inferno',
which I suspect is where almost all of the
computation time is coming from.
Instead of doing:
divChng <- rbind(divChng,c(datTS$ts[1], SEG[j], DC, GRW,
max(datTS$iter)))
it would be much better to create 'divChng' to
be the final length and then
The small example below works lighting-fast; however, when I run the same
script on my real problem, a 1Gb text file, the for loops have been running
for over 24 hrs and I have no idea if the processing is 10% done or 90%
done. I have not been able to figure out a betteR way to code up the
materia
I sent a post yesterday that I found out why my function didn't work. It's
ok now it works.
Thank you all.
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__
No idea how this relates to what you said originally but glad you got
it all worked out.
And let us all reiterate: really, don't use nested for loops...there's
a better way: promise!
Michael
On Sat, Nov 5, 2011 at 2:20 PM, nick_pan wrote:
> I found the way out - it was because the borders of th
Bert, this is not helpful. Since for loops and apply functions are not
vectorized, why are you admonishing Carl that vectorizing doesn't always speed
up algorithms? He didn't reference apply functions as being vectorized. But you
seem to be doing so.
I would assert that vectorizing DOES always
I found the way out - it was because the borders of the vectors was close
enough thats why I had the same result while I was adding points to the
sequence. The example I gave was irrelevant but I made in order to find out
that the problem was.
Thank you all for your answers.
--
View this message
Carl: "Almost anything you can do in a for() loop can be done easier and
faster with vectorization.-- "
That is false: while this is certainly true for a great many basic
vectorized operations, it is certainly false for most other things --
simulations are a typical example. Note that __ply type o
You need to define "l" as a dimensioned object , either a vector or an array,
and then assign the value of your calculation to the correctly indexed
"location" in that object. Otherwise you are just overwriting the value each
time through the loop. Use these help pages (and review "Introduction
If in fact this is homework, you will do yourself, your classmates, and
possibly your teacher if you let them know that, at least in R, almost
anything you can do in a for() loop can be done easier and faster with
vectorization. If you teacher can't comprehend this, get him fired.
a<-c(4,6,3)
Why do you need to do it with nested for loops? It is of course possible - and
I hinted how to do it in my first email - but there's no reason as far as I can
see to do so, particularly as a means of MLE. Sounds suspiciously like
homework...
Michael
On Nov 4, 2011, at 10:14 PM, nick_pan wrote
Thank you , this works but I have to do it with nested for loops...
Could you suggest me a way ?
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Your problem is that you redefine l each time through the loops and
don't record old values; you could do so by using c() for
concatenation, but perhaps this is what you are looking for:
exp(rowSums(log(expand.grid(V1, V2, V3
Hope this helps,
Michael
On Fri, Nov 4, 2011 at 7:49 PM, nick_pan
Hi all , I have written a code with nested "for" loops .
The aim is to estimate the maximum likelihood by creating 3 vectors with the
same length( sequence )
and then to utilize 3 "for" loops to make combinations among the 3 vectors ,
which are (length)^3 in number , and find the one that maximiz
What do you want to do with the data being genereated? In the loop
you have, it will just return the last value generated. Let me ask my
favorite question: "What is the problem you are trying to solve". If
you get a memory problem with expand.grid, then if you are trying to
store the values in t
Le 05/07/10 23:06, Senay ASMA a écrit :
Dear Admin,
I will appreciate if you advise me an effective way to write the following R
code including nested for loops. I cannot do it by using expand.grid
function because it results with memory allocation problems.
Thanks for your time and considerati
Dear Admin,
I will appreciate if you advise me an effective way to write the following R
code including nested for loops. I cannot do it by using expand.grid
function because it results with memory allocation problems.
Thanks for your time and consideration.
for(d1 in 0:n){
for(d2 in 0:n){
for(d3
k is the lag.
Baloo
--- On Tue, 12/22/09, ONKELINX, Thierry wrote:
From: ONKELINX, Thierry
Subject: RE: [R] Nested For loops
To: "baloo mia" , r-help@r-project.org
Date: Tuesday, December 22, 2009, 1:00 AM
Baloo,
Why don't you use the built-in acf
In the ACF(nlme) the normalization of the numerator has been done by N and I
want to normalize it by N-k, where N is the observations and k is the lag.
Baloo
--- On Tue, 12/22/09, ONKELINX, Thierry wrote:
From: ONKELINX, Thierry
Subject: RE: [R] Nested For loops
To: "baloo mia"
~ John Tukey
-Oorspronkelijk bericht-
Van: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] Namens
baloo mia
Verzonden: dinsdag 22 december 2009 2:07
Aan: r-help@r-project.org
Onderwerp: [R] Nested For loops
Dear R experts,
Might be very simple question to ask but would be insightful
Dear R experts,
Might be very simple question to ask but would be insightful. As the same story
of nested "for loops". following is the code that I am using to get the
autocorrelation function of the sample data. I have tried to get rid of for
loops but since I am touching R after such a long t
On Tue, Jul 14, 2009 at 2:29 PM, Gabor
Grothendieck wrote:
> seq. <- function(from, to) seq(from = from, length = max(0, to - from + 1))
Really nice! Thank you!
--
Michael Knudsen
micknud...@gmail.com
http://lifeofknudsen.blogspot.com/
__
R-help@r-pr
On Tue, Jul 14, 2009 at 1:56 PM, David Winsemius wrote:
>> temp[ upper.tri(temp) ]
> [1] 7 13 14 19 20 21 25 26 27 28 31 32 33 34 35
Thanks! I didn't know about that function; it certainly makes things a
lot easier. For example, until now I have used the following, homemade
expression
(1:N^2)[
Try this:
seq. <- function(from, to) seq(from = from, length = max(0, to - from + 1))
seq.(11, 10)
On Tue, Jul 14, 2009 at 1:38 AM, Michael Knudsen wrote:
> Hi,
>
> I have spent some time locating a quite subtle (at least in my
> opinion) bug in my code. I want two nested for loops traversing
On Jul 14, 2009, at 2:25 AM, Michael Knudsen wrote:
On Tue, Jul 14, 2009 at 8:20 AM, Michael
Knudsen wrote:
What do you mean? It looks a like a very general solution to me.
Just got an email suggesting using the functions col and row. For
example
temp = matrix(c(1:36),nrow=6)
which(co
On Tue, Jul 14, 2009 at 8:20 AM, Michael Knudsen wrote:
> What do you mean? It looks a like a very general solution to me.
Just got an email suggesting using the functions col and row. For example
temp = matrix(c(1:36),nrow=6)
which(col(temp)>row(temp))
This gives the indices (in the matrix vie
On Tue, Jul 14, 2009 at 8:03 AM, Moshe Olshansky wrote:
> Make it
> for (i in 1:9)
Thanks. That's also how I solved the problem myself. I just somehow
think it makes my code look rather clumsy and opaque. Maybe I just
have to get used to this kind of nasty tricks.
> This is not the general solut
Make it
for (i in 1:9)
This is not the general solution, but in your case when i=10 you do not want to
do anything.
--- On Tue, 14/7/09, Michael Knudsen wrote:
> From: Michael Knudsen
> Subject: [R] Nested for loops
> To: r-help@r-project.org
> Received: Tuesday, 14 July, 2009,
> -Original Message-
> From: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] On Behalf Of Michael Knudsen
> Sent: Monday, July 13, 2009 10:39 PM
> To: r-help@r-project.org
> Subject: [R] Nested for loops
>
> Hi,
>
> I have spent some ti
Hi,
I have spent some time locating a quite subtle (at least in my
opinion) bug in my code. I want two nested for loops traversing the
above-diagonal part of a square matrix. In pseudo code it would
something like
for i = 1 to 10
{
for j = i+1 to 10
{
// do something
}
}
However,
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