search for: spowers

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Hi everyone, I was wondering whether extension of the current spower function for Hmisc were existing? My current focus is to calculate sample size based on the log-rank test with more than 2 groups (with/without trend) Taking into account the loss of follow up and the accrual processes. A SPSS library (ART) is existing but can't find anything in R Any information is welcome ! Many

Dear all, I'm looking for someone that help me to write an R function to simulate survival data under complex situations, namely time-varying hazard ratio, marginal distribution of survival times and covariates. The algorithm is described in the reference below and it should be not very difficult to implement it. However I tried but without success....;-( Below there the code that I used; it

I know that mvrnorm from MASS (generously provided by Profs. Venables and Ripley) can be used to generate multivariable normal data that can be used in a linear regression with certain desired characteristics (e.g. a given mean for each variable as well as a given variance-covariance pattern). Is there any similar facility that can be used to generate data for (1) a logistic regression and (2) a

Dear R friends, this is an off-topic question. Could you please point me in ways (e.g., references or even R code) for simulating time varying covariates in a survival analysis setting. Thanks in advance for any responses. yours sincerely, Jin

I would like to do some power estimations for a log-rank two sample test and cpower seems to fit the bill. I am getting confused though by the man page and what the arguments actually mean. I am also not sure whether cpower takes into account censoring or not. Could anyone provide a simple example of how I would get the power for a set control/non-control clinical trial where censoring occurs at

It returns a chi-squared statistic with one degree of freedom. -- David Winsemius -------------- Original message ---------------------- From: Timthy Chang <henchao.chang at gmail.com> > > > >See the cpower() and spower() functions in Frank Harrell's Hmisc package > >on CRAN. > > > >HTH, > > > >Marc Schwartz > > How to calculate the

Does anyone have any ideas how I could do a power calculation for a log rank test. I would like to know what the suggested sample sizes would be to pick a difference when the control to active are in a ratio of 80% to 20%. Thanks Dan -- ************************************************************** Daniel Brewer, Ph.D. Institute of Cancer Research Email: daniel.brewer at icr.ac.uk

Hi folks, Using R Version 1.6.2 (2003-01-10) on SuSE Linux 7.2, I just installed Hmisc_1.5-3.tar.gz and Design_1.1-5.tar.gz These were taken from http://hesweb1.med.virginia.edu/biostat/s/library/r Checked the dependencies: Hmisc: grid, lattice, mva, acepack -- all already installed Design: Hmisc, survival -- survival already installed, so installed Hmisc first All seems to go

Dear R users, I am not asking questions specifically on R, but I know there are many statistical experts here in the R community, so here it goes my questions: Freedman (1982) propose an approximation of sample size/power calculation based on log-rank test using the formula below (This is what nQuery does): (Z(1-?/side)+Z(power))^2*(hazard.ratio+1)^2 N =

(This is releveant information to the one that Alex Moore just posted, but I'm not subscribed yet so I can't properly reply to that thread. Sorry for creating a new one.) I've got a crash in dovecot-imap when trying to list the inbox on a nonexistant directory. I'm not sure how it should be handled, but basically it's only happening when the directory in imap's MAIL

Hi , I just recently installed OpenSSH_3.0.2p1 on a HP-UX box. The ssh works fine but the sftp is not. There is a firewall in between both the machine. Only SSH port is allowed from the source host to the destination machine. ssh works fine across the firewall. Below is the log. Thanks in advance . ~~~~~~~~~~~~~~~~~~~~~~~~~~~` <ixos2:/home/smorrx> sftp spdns1 Connecting to spdns1... smorrx