search for: weibul

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2012 Feb 21
HELP ERROR Weibull values must be > 0
GUYS, I NEED HELP WITH ERROR: library(MASS) > dados<-read.table("mediaRGinverno.txt",header=FALSE) > vento50<-fitdistr(dados[[1]],densfun="weibull") Erro em fitdistr(dados[[1]], densfun = "weibull") : Weibull values must be > 0 WHY RETURN THIS ERROR? WHAT CAN I DO? BEST REGARDS [[alternative HTML version deleted]]
2005 Nov 24
Survreg Weibull lambda and p
Hi All, I have conducted the following survival analysis which appears to be OK (thanks BRipley for solving my earlier problem). > surv.mod1 <- survreg( Surv(timep1, relall6)~randgrpc, data=Dataset, dist="weibull", scale = 1) > summary(surv.mod1) Call: survreg(formula = Surv(timep1, relall6) ~ randgrpc, data = Dataset, dist = "weibull", scale = 1) Value Std. Error z p (Intercept) 7.36 0.259 28.42 1.27e-177 randgrpc -0.59 0.156 -3.80 1....
2002 Jan 17
weibull in R
Hi all I try to make a weibull survival analysis on R. I know make this on GLIM, and now I try to make the GLIM exercice GLEX8 on R to learning and compare the test. The variables are: time censor group bodymass In GLIM I make: $calc %s=1 $ to fit weibull rather than exponential $input %pcl weibull $ $macro model group*bodyma...
2005 Nov 22
Weibull and survival
Hi I have been asked to provide Weibull parameters from a paper using Kaplan Meir survival analysis. This is something I am not familiar with. The survival analysis in R works nicely and is the same as commercial software (only the graphs are superior in R). The Weibull does not and produces an error (see below). Any ideas why thi...
2012 Apr 22
Hi all, I am trying to run Weibull PH model in R. Assume in the data set I have x1 a continuous variable and x2 a categorical variable with two classes (0= sick and 1= healthy). I fit the model in the following way. Test=survreg(Surv(time,cens)~ x1+x2,dist="weibull") My questions are 1. Is it Weibull PH model or...
2010 Jan 28
Problems with fitdistr
Hi, I want to estimate parameters of weibull distribution. For this, I am using fitdistr() function in MASS package.But when I give fitdistr(c,"weibull") I get a Error as follows:- Error in optim(x = c(4L, 41L, 20L, 6L, 12L, 6L, 7L, 13L, 2L, 8L, 22L, : non-finite value supplied by optim Any help or suggestions are mos...
2005 Mar 14
Parameters of Weibull regression
Dear list, dear Frank, I try to fit a Weibull survival regression model with package Design: sclear <- psm(sobj~V1+V2,dist="weibull") sobj is a one-dimensional survival object (no event indicators), V1 and V2 are factors. I get the following result: Parametric Survival Model: Weibull Distribution psm(formula = sobj ~ V1 + V...
2012 Mar 06
Scale parameter in Weibull distribution
Hi all, I'm trying to generate a Weibull distribution including four covariates in the model. Here is the code I used: T = rweibull(200, shape=1.3, scale=0.004*exp(-(-2.5*b1+2.5*b2+0.9*x1-1.3*x2)/1.3)) C = rweibull(n, shape=1.5, scale=0.008) #censoring time time = pmin(T,C) #observed time is min of censored and true event = time=...
2001 Jul 02
nls newbie: help approximating Weibull distribution
Hi folks, I tried to retain the Weibull distribution using the `nls' function and proceeding along the lines of the example provided in the `SSweibull' help (at least I thought so): t <- (1:200)/100 v <- pweibull(t, shape=3, scale=1) df <- data.frame(Time=t, Value=v) Asym <- 1.0; Drop <- 1.0; lrc <- 0;...
2013 Nov 03
Comparison of two weibull distributions
Hello, How can I do a test of two weibull distributions? I have two weibull distribution sets from two wind datasets in order to check whether they are same. I thought 2 sample t-test would be applicable but I couldn't find any ways to do that on the Internet. Does anyone know what type of test is applicable to my purpose? and what R...
2008 Oct 28
Fitting weibull and exponential distributions to left censoring data
Dear R-users I have some datasets, all left-censoring, and I would like to fit distributions to (weibull,exponential, etc..). I read one solution using the function survreg in the survival package. i.e survreg(Surv(...)~1, dist="weibull") but it returns only the scale parameter. Does anyone know how to successfully fit the exponential, weibull etc... distributions to left-censoring data?...
2009 Nov 13
survreg function in survival package
...function with standard error, z, p.value etc? Does it mean that intercept was fitted with the covariates? Does Value column represent coefficients or some thing else? Regards, ------------------------------------------------- tmp = survreg(Surv(futime, fustat) ~ + rx, ovarian, dist='weibull',scale=1) > summary(tmp) Call: survreg(formula = Surv(futime, fustat) ~ + rx, data = ovarian, dist = "weibull", scale = 1) Value Std. Error z p (Intercept) 6.962 1.322 5.267 1.39e-07 -0.433 0.587 -0.738 4.61e-01 rx...
2009 Jun 05
Fitting a Weibull Distribution
How do you fit a Weibull distribution in R?
2007 Jun 08
glm() for log link and Weibull family
I need to be able to run a generalized linear model with a log() link and a Weibull family, or something similar to deal with an extreme value distribution. I actually have a large dataset where this is apparently necessary. It has to do with recovery of forensic samples from surfaces, where as much powder as possible is collected. This apparently causes the results to confo...
2010 Nov 15
interpretation of coefficients in survreg AND obtaining the hazard function
1. The weibull is the only distribution that can be written in both a proportional hazazrds for and an accelerated failure time form. Survreg uses the latter. In an ACF model, we model the time to failure. Positive coefficients are good (longer time to death). In a PH model, we model the death rate. Pos...
2009 Dec 06
MLE in R
Hi, dear R users I am a newbie in R and I need to use the method of meximum likelihood to fit a Weibull distribution to my survival data. I use "optim" as follows: optim(c(1.14,0.25),,mydata=mydata,method="L-BFGS-B",hessian = TRUE) My question is: how do I setup the constraints that the two parametrs of Weibull to be pisotive? Many thanks! Any comments are greatly...
2009 Jan 04
Bivarite Weibull Distribution
HI Every one Could some one provide me definitions of following bivariate distributions gamma, exponencial, Weibull, half-normal , Rayleigh, Erlang,chi-square thanks A.S. Qureshi
2013 Oct 28
"Optimization fail" error from fitdistr (Weibull distribution)
...40 13 41 9 42 5 43 2 R codes to calculate shape and scale are described below: Pine.windfrequency.4weeks<-read.table("C:/Users/kmoon/Documents/Pine_frequency_4weeks.csv",header=TRUE,sep=",") fitdistr(Pine.windfrequency.4weeks$Frequency, densfun="weibull") I have got an error message when I was using 'fitdistr' function "Error in fitdistr(Pine.windfrequency.4weeks$Frequency, densfun = "weibull") : optimization failed" Please help me calculating shape and scale of weibull distribution. And please understa...
2006 Apr 26
cdf of weibull distribution
Hi, I have a data set which is assumed to follow weibull distr'. How can I find of cdf for this data. For example, for normal data I used (package - lmomco) >cdfnor(15,parnor(lmom.ub(c(df$V1)))) Also, lmomco package does not have functions for finding cdf for some of the distributions like lognormal. Is there any other package, which...
2003 Jul 28
Optimization failed in fitting mixture 3-parameter Weibull distri bution using fitdistr()
Dear All; I tried to use fitdistr() in the MASS library to fit a mixture distribution of the 3-parameter Weibull, but the optimization failed. Looking at the source code, it seems to indicate the error occurs at if (res$convergence > 0) stop("optimization failed"). The procedures I tested are as following: >w3den <- function(x, a,b,c) {c/b*((x -a...