Displaying 20 results from an estimated 3000 matches similar to: "Is there a similar R function like "stpower" in STATA"
2011 Jun 20
2
Error of Cross Validation
Dear R users:
Recently, I tried to write a program to calculate cross-validated predicted
value.
My sources are as follows. However, the R reported an error.
Could you please check the sources? Thanks.
set.seed(100)
x<-rnorm(100)
y<-sample(rep(0:1,50),replace=T)
dat<-data.frame(x,y)
library(rms)
fito<-lrm(y~x)
preo<-predict(fito)
pre<-matrix(NA,nrow=100,ncol=200)
for (i in
2009 Sep 12
2
could not find function "Varcov" after upgrade of R?
After upgrading R to 2.9.2, I can't use the anova() fuction.
It says "could not find function "Varcov" ".
What's wrong with my computer? Help needed, thanks!
Yao Zhu
Department of Urology
Fudan University Shanghai Cancer Center
No. 270 Dongan Road, Shanghai, China
[[alternative HTML version deleted]]
2010 Jan 21
3
cross validation function translated from stata
Hi, everyone:
I ask for help about translating a stata program into R.
The program perform cross validation as it stated.
#1. Randomly divide the data set into 10 sets of equal size, ensuring equal
numbers of events in each set
#2. Fit the model leaving out the 1st set
#3. Apply the fitted model in (2) to the 1st set to obtain the predicted
probability of a prostate cancer diagnosis.
#4. Repeat
2011 Apr 22
2
How to answer the question about transitive correlation?
Hi, everyone. I know it may be a basic statistical question. But I can't
find a good answer.
I have a question raised by one of the reviewers.
Factor A expression was strongly correlated with B expression (chi-square)
in this series. Prior reports by the same authors showed that B expression
strongly correlated with survival (Log-rank). Please provide an explanation
why then were the results
2013 Feb 11
1
how to plot growth chart like this
Dear R-users
I want to generate a growth chart like this:
http://php.med.unsw.edu.au/embryology/images/9/9a/WHO-XX_length_birth_to_2_years.png
can you give some suggestions about the functions I should use?
Thanks
*Yao Zhu*
*Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China*
[[alternative HTML version deleted]]
2011 Jul 15
1
validate survival with val.surv
Dear R users:
I want to externally validate a model with val.surv.
Can I use only calculated survival (at 1 year) and actual survival?
Or I needed the survival function and actual survival.
Thanks
*Yao Zhu*
*Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China*
[[alternative HTML version deleted]]
2011 Sep 01
1
How to retrieve bias-corrected probability from calibrate.rms
Dear R users:
In Prof. Harrell's library rms, calibrate.rms plot the Bias-corrected
Probability and Apparent Probability.
The latter one can be retrieved from class calibrate.default. But how to
retrieve the former one.
BW
*Yao Zhu*
*Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China*
[[alternative HTML version deleted]]
2011 May 01
1
Different results of coefficients by packages penalized and glmnet
Dear R users:
Recently, I learn to use penalized logistic regression. Two packages
(penalized and glmnet) have the function of lasso.
So I write these code. However, I got different results of coef. Can someone
kindly explain.
# lasso using penalized
library(penalized)
pena.fit2<-penalized(HRLNM,penalized=~CN+NoSus,lambda1=1,model="logistic",standardize=TRUE)
pena.fit2
2009 Jul 26
1
How to add 95% confidence intervals in the calibration plot?
Dear experts:
I am a newbie to R. Recently, I try to make prediction models with R and the
Design library.
I have read Prof. Harrell's excellent book. But I did not quite understand.
I have two problems about the validation and calibration of prediction
models:
1. Can someone explain the results outputted by the validate() function? How
to get 95% of c-value of validate?
2. How to add 95% ci
2011 May 08
1
question about val.surv in R
Dear R users:
I tried to use val.surv to give an internal validation of survival
prediction model.
I used the sample sources.
# Generate failure times from an exponential distribution
set.seed(123) # so can reproduce results
n <- 1000
age <- 50 + 12*rnorm(n)
sex <- factor(sample(c('Male','Female'), n, rep=TRUE, prob=c(.6, .4)))
cens <- 15*runif(n)
h
2010 Oct 13
1
bootstrap in pROC package
Dear useRs:
I use pROC package to compute the bootstrap C.I. of AUC.
The command was as follows:
roc1<-roc(all$D,all$pre,ci=TRUE,boot.n=200)
However, the result was:
Area under the curve: 0.5903
95% CI: 0.479-0.7016 (DeLong)
Why the C.I. was computed by the Delong Method?
Yao Zhu
Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China
[[alternative HTML version
2011 Feb 26
2
tansformation of variables in cph from rms package
Dear all:
I have used the cph function in the rms package.
log10 was used to transform the variables, as follows:
fit<-cph(pfsurv~log10(x1)+log10(x2),x=T,y=T,surv=T)
after I run the nomogram function.
I found "variable limits and transformations are such that an infinite axis
value has resulted."
How to add variable limits in the nomogram function?
Thanks a lot
*Yao Zhu*
2011 Jun 04
1
nonparametric logistic regression based on locally weighted scatterplot smoothing (lowess)
Dear UseRs:
Recently, I have read an article regarding the association between age and
lymph node metastases.
http://jco.ascopubs.org/content/27/18/2931.long
In statistical analysis, the authors stated "Because a nonlinear
relationship between age and lymph node involvement was expected based on
existing literature, lymph node involvement was also regressed on age using
nonparametric
2011 Oct 10
0
how to extent the improveProb for survival data
Dear R users
Function improveProb in the rms library calculate NRI and IDI for
predictions of binary outcome.
Do anyone extent its use in survival data?
Many thanks.
*Yao Zhu*
*Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China*
[[alternative HTML version deleted]]
2011 Aug 01
2
How to make a nomogam and Calibration plot
Dear R users,
I am a new R user and something stops me when I try to write a academic
article. I want to make a nomogram to predict the risk of prostate cancer
(PCa) using several factors which have been selected from the Logistic
regression run under the SPSS. Always, a calibration plot is needed to
validate the prediction accuracy of the nomogram.
However, I tried many times and read a lot of
2018 May 29
2
LLVM Social - Beijing: May 19th, 2018
在 2018年05月29日 14:58, mayuyu.io 写道:
> Any hint on the date of LLVM Social ShangHai?
Wu Wei scheduled July 1th http://hellollvm.org/
>
> Zhang
>
>> 在 2018年5月29日,14:22,Leslie Zhai via llvm-dev <llvm-dev at lists.llvm.org> 写道:
>>
>> Hi Chris,
>>
>> Thanks for your response!
>>
>> Wu Wei made this happen! and he is organizing LLVM social in
2018 May 29
0
LLVM Social - Beijing: May 19th, 2018
Hope live broadcast ! <br/><br/>Thanks,<br/>yaoxiao
在 2018-05-29 15:02:30,"Leslie Zhai via llvm-dev" <llvm-dev at lists.llvm.org> 写道:
>
>
>在 2018年05月29日 14:58, mayuyu.io 写道:
>> Any hint on the date of LLVM Social ShangHai?
>Wu Wei scheduled July 1th http://hellollvm.org/
>
>
>>
>> Zhang
>>
>>> 在
2010 Jun 03
1
Continous variables with implausible transformation?
Dear r users
I have a question in coding continuous variables in logistic regression.
When "rcs" is used in transforming variables, sometime it gives implausible
associations with the outcome although the model x2 is high.
So what's your tips and tricks in coding continuous variables.
P.S. How to code variables as linear+square in the formula such as lrm.
lrm(y~x+sqrt(x))
2007 Jun 21
1
A HTB problem
My hardware is a Linksys AP with MIPS 300MHz and Linux kernel 2.4.20.
The traffics are from two LAN switch ports to WAN port. And the traffics
are generate at a rate of 80Mbit. So the total traffic to WAN port is
160Mbit. The shaping works well that the traffic to WAN port is about
50/30Mbit according to configuration. But the priority seems strange
when the root rate is 50Mbit.
When the root
2012 Dec 20
2
how to read different files into different objects in one time?
Dear All
I have a lot of files in a directory as follows:
"02-03.txt" "03-04.txt" "04-05.txt" "05-06.txt" "06-07.txt"
"07-08.txt" "08-09.txt"
"09-10.txt" "G0.txt" "G1.txt" "raw_ped.txt"
..........................
I want to read them into different objects according