Displaying 20 results from an estimated 393 matches for "gradient".

2007 Dec 03

0

12 commits - libswfdec/Makefile.am libswfdec/swfdec_as_strings.c libswfdec/swfdec_as_types.c libswfdec/swfdec_as_types.h libswfdec/swfdec_gradient_pattern.c libswfdec/swfdec_gradient_pattern.h libswfdec/swfdec_movie_as_drawing.c libswfdec/swfdec_pattern.c

libswfdec/Makefile.am | 2
libswfdec/swfdec_as_strings.c | 17 +
libswfdec/swfdec_as_types.c | 16 +
libswfdec/swfdec_as_types.h | 2
libswfdec/swfdec_gradient_pattern.c | 129 +++++++++++++++
libswfdec/swfdec_gradient_pattern.h | 67 +++++++
libswfdec/swfdec_movie_as_drawing.c | 172 +++++++++++++++++++-
libswfdec/swfdec_pattern.c | 123 --------------
test/imag...

2011 Aug 29

3

gradient function in OPTIMX

...r, when I use OPTIMX with BFGS( or spg), I've got the
following an error message.
----------------------------------------------------------------------------------------------------
> optimx(par=theta0, fn=obj.fy, gr=gr.fy, method="BFGS",
> control=list(maxit=10000))
Error: Gradient function might be wrong - check it!
----------------------------------------------------------------------------------------------------
I checked and checked my gradient function line by line. I could not find
anything wrong.
Is it a bug or something? I prefer OPTIMX, so I'd like to know...

2008 Apr 22

2

optimization and gradient

Dear all,
I am using the functions 'optim' and 'nlminb'. For both, you can provide
a function which computes the gradient of the objective function (to
enhance speed and precision). In my case, both the objective function
and the gradient take time to be computed and share many common
computations (similar matrix, products, etc...). Therefore, I have to
compute these quantities twice which slows down the procedure...

2011 Aug 31

1

Gradients in optimx

Hi Reuben,
I am puzzled to note that the gradient check in "optimx" does not work for you. Can you send me a reproducible example so that I can figure this out?
John - I think the best solution for now is to issue a "warning" rather than an error message, when the numerical gradient is not sufficiently close to the user-speci...

2004 Mar 29

1

calculate length of gradient ?

...tests=MSGID_FROM_MTA_HEADER,RCVD_IN_BL_SPAMCOP_NET autolearn=no version=2.63
Dear r-help list,
my question is about ordination technics:
To decide using a linear model response or a unimodal model response,
in Canoco (software for ordination technics)
you can calculate a so-called "length of gradient".
(from Canoco Help file:)
> The length of gradient is a measure of how unimodal the species
> responses are along an ordination axis. It is the range of the
> sample scores divided by the average within-species standard
> deviation along the axis. The gradient length is expressed...

2013 Mar 14

2

question about nls

Hi,all:
I met a problem of nls.
My data:
x y
60 0.8
80 6.5
100 20.5
120 45.9
I want to fit exp curve of data.
My code:
> nls(y ~ exp(a + b*x)+d,start=list(a=0,b=0,d=1))
Error in nlsModel(formula, mf, start, wts) :
singular gradient matrix at initial parameter estimates
I can't find out the reason for the error.
Any suggesions are welcome.
Many thanks.
[[alternative HTML version deleted]]

2005 Nov 16

2

numericDeriv

I have to compute some standard errors using the delta
method and so have to use the command "numericDeriv"
to get the desired gradient. Befor using it on my
complicated function, I've done a try with a simple
exemple :
x <- 1:5
numericDeriv(quote(x^2),"x")
and i get :
[1] 1 8 27 64 125 216
attr(,"gradient")
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] Inf 0 0 NaN 0 0
[2,] 0 0 0...

2017 Oct 24

3

draw a circle with a gradient fill

Hi all,I would like to draw a simple circle where the color gradient follows the rule color = 1/(r^2) where r is the distance from the circle. I would also like to add a color bar with values going from -40 to -110 (and associate those with the color gradient that fills the circle).
So far I experiemented with draw circle install.packages('plotrix')requi...

2009 Apr 26

1

Stochastic Gradient Ascent for logistic regression

Hi. guys,
I am trying to write my own Stochastic Gradient Ascent for logistic
regression in R. But it seems that I am having convergence problem.
Am I doing anything wrong, or just the data is off?
Here is my code in R -
lbw <-
read.table("http://www.biostat.jhsph.edu/~ririzarr/Teaching/754/lbw.dat"
, header=TRUE...

2013 Oct 03

2

SSweibull() : problems with step factor and singular gradient

SSweibull() : problems with step factor and singular gradient
Hello
I am working with growth data of ~4000 tree seedlings and trying to fit non-linear Weibull growth curves through the data of each plant. Since they differ a lot in their shape, initial parameters cannot be set for all plants. That’s why I use the self-starting function SSweibull().
How...

2011 Feb 15

2

"Error : singular gradient matrix at initial parameters estimates"

Dear all,
I am a fresh user of R and I already face to problems that I don't
understand.
In the use of the function nls(), I systematically have an error message :
"Singular gradient matrix at initial parameters estimates".
I tried to use nls() on a set of data that I subseted from a bigger matrix
data. I wish to fit a gaussian on these points (spectrum) and draw this fit
on the plot.
Is this possible? Why do I always have this error message when using nls() ?
Thank you f...

2008 Apr 08

2

diagonally fill a rectangle with color gradient

Hi,
Is it possible to diagonally fill a rectangle with a color gradient? I
noticed that the gradient.rect of plotrix could fill a rect either up and
down or from side to side. I am looking for something similar but fills
diagonally instead, e.g., from the upper left corner to the bottom right.
Does anyone know how to do it in R?
Thanks,
--
Tom
[[alternative HTML v...

2006 Jun 19

0

help on nlm (gradient) (fwd)

...ymore. Figured it out.
Thanks for everything.
Luz
---------- Forwarded message ----------
Date: Sun, 18 Jun 2006 23:12:25 -0600 (MDT)
From: Luz Maria Palacios Derflingher <palacios at math.ucalgary.ca>
To: r-help at lists.R-project.org
Cc: r-help at stat.math.ethz.ch.
Subject: help on nlm (gradient)
Hello.
I am having some trouble using nlm in R for windows version 2.2.1. I have to
minimise a function which includes in its insides the evaluation of
integrals through the "adapt" function.
In order to make R work less, I calculated the gradient and coded it. I made
sure that the...

2007 Feb 07

1

Singular Gradient

I tried to fit data with the following function:
fit<-nls(y~ Is*(1-exp(-l*x))+Iph,start=list(Is=-2e-5,l=2.3,Iph=-0.3
),control=list(maxiter=500,minFactor=1/10000,tol=10e-05),trace=TRUE)
But I get only a singular Gradient warning...
the data can by found attached(there are two sampels of data col 1/2 and
3/4).
I tried to fix it by chanching the start parameters but that didn't solve
the problem.
Would it be a possibiliti to use the selfstart Model? How?
Thanks for any answers
This

1999 Nov 24

0

nlm gradient and hessian

Out of curiosity, I have tried, without success, to use the new
facility in nlm to specify the gradient and hessian. (It is many years
since I had a problem simple enough to make analytic derivation of
these worthwhile.) The help now says that the function must have
attributes with these names but gives no indication as to what should
be in the attributes. The online example and demo do not use the n...

2008 Apr 28

1

Making color gradient

Hi
I would like to make a color bar with a gradient of colors that represent
values between 0-1. I used the gradient.rect function in plotrix to make
the actually color bar but I don't know how to put a range of values (0-1)
next to the color bar. How do I do this?
Thanks
Zarrar
--
Zarrar Shehzad
Research Assistant
NYU Child Study Center
21...

2018 Apr 05

2

Obtain gradient at multiple values for exponetial decay model

...,16
280,12
320,10
360,9
400,7
graphdata<-read.csv('~/tmp/data.csv')
graphmodeld<-lm(log(graphdata[,2])~graphdata[,1])
graphmodelp<-exp(predict(graphmodeld))
plot(graphdata[,2]~graphdata[,1])
lines(graphdata[,1],graphmodelp)
Please what is the function and syntax to obtain gradient values for the model curve at various requested values, e.g.:
when graphdata[,1] at values = 100, 250, 350 ?

2015 Sep 04

9

[RFC] Refinement of convergent semantics

...this operation may not be made control dependent on any additional values (aka may not be sunk into a condition)
nospeculate - this operation may not be added to any program trace on which it was not previously executed (same as notrap?)
Most of today’s convergent operations (barriers, arithmetic gradients) would continue to be marked only as convergent. The new semantics would allow full loop unrolling, and provide clarity on which loop unswitching operations are allowed, examples below.
The one case where nospeculate would also be needed is in the case of texture fetches that compute implicit gr...

2018 Feb 05

1

Package sgd

A web search on "gradient descent R" also brought up a bunch of stuff. Is
any of this what you want?
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 )...

2018 Apr 05

4

Obtain gradient at multiple values for exponetial decay model

...9
This prompted to think that interpolation is required, but the function 'approx' only seems to perform constant interpolation.
Is the correct thinking to find a function to perform interpolation, then find/write a function to differentiate the model at a specific value of x, to find gradient at that point?