similar to: finding roots (Max Like Est)

Dear All, Is it possible to get confidence intervals for Harrell's concordance index or, equivalently, Somer's D using the rms package or in some other way ? I have survival data it would be the c-index in the Cox model setting Many thanks Dr Bernard North Statistical Consultant Statistical Advisory Service Advice and Courses on Research Design and Methodology Imperial College South

Hi, I'm trying to use Robust non-linear regression to fit dose response curves. Maybe I didnt look good enough, but I dind't find robust methods for NON linear regression implemented in R. A method that looked good to me but is unfortunately not (yet) implemented in R is described in http://www.graphpad.com/articles/RobustNonlinearRegression_files/frame.htm

Dear R help My problem is very similar to the analysis detailed here. If we use the mayo dataset provided with the survivalROC package the estimate for Somer's Dxy is very negative -0.56. The Nagelkerke R2 is positive though 0.32. I know there is a difference between explained variation and predictive ability but I am surprised there is usch a difference given that even a non predictive model

Hello, I have being trying to estimate the parameters of the?generalized?exponential distribution. The random number generation for the GE distribution is?x<-(-log(1-U^(1/p1))/b), where U stands for uniform dist. The data i have generated to estimate the parameters is right censored and the code is given below; The problem is that, the newton-Raphson approach isnt working and i do not know what

I am having trouble getting a loop to work for the following problem. Any help would be much appreciated. Thanks. I need to find the slope and intercept from the linear regression of Drug Level on Day by Participant. There are a total of 37 Participants. I need to store the Participant, Label, Slope, and Intercept in a new data frame. This data is ordered by Participant number 37 total

Dear List, This is just a programming problem which i cannot seem to figure out. I am trying to get a set of power from a test (say, kolmogorov smirnov) out of a distribution (say, G-K distribution) as follows. I am trying to reduce to pain of writing the whole set of data points (p# below) using "for" loop. However, I seem to have some problem in it as the output "M" does not

Hi, Why sum() on a 10-item vector produces a different value than its counterpart on a 2-item vector? I understand the problems related to the arithmetic precision in storing decimal numbers in binary format, but shouldn't the errors be equal regardless of the method used? See my example: > options(digits=22) > x=rep(.1,10) > x [1] 0.10000000000000001 0.10000000000000001

I am working on minimization of sum of squared errors for a problem that has 2 box-constrained parameters. I got the solution for this problem using "L-BFGS-B" method in optim function using an R code as res<-optim(par=c(parInit), fn=myFunction, method = c("L-BFGS-B"), lower = parMin, upper = parMax,

Dear all, I have a sample with 920 observations. I want to create a loop which takes 300 of these observations for the prediction and the rest to estimate the model. My idea was to create something like this: cs.training.dat <- read.table... cs.training.dat_sub1 <- subset(cs.training.dat, Income>10) cs.training.dat_sub2 <- subset(cs.training.dat_sub1, Dept.Ratio<=1)

Does anyone know precisely what is different about the arithmetic and/or storage of double precision floating point to produce the following differences between the Sun and Windows versions (Splus 6 on the same Windows 2000 machine gives the same results as Solaris)? R 1.6.1, Sun Solaris, gcc + an old Sun f77 > options(digits=20) > 1+(1/2^53+1/2^106) [1] 1 > 1+(1/2^53+1/2^105) [1]

I'm having a function of the form 1> f<-function(x){ 1+ 1+ return(x^p) 1+ 1+ } ,and I would like to integrate it with respect to x, where p should be any constant. One way would be to set a value for p globally and then call integrate function: p=2 integrate(f, lower = -1, upper = 1) However, I would like to use 'integrate' inside a function, so I could call it passing

Dear r-users, I would like to convert my Matlab code to R-code, however it dies not work as expected.  Hope somebody can help me to match Matlab and r codes. R code: rr <- function(r,cxn) { tol <- 1E-4; for(i in 1:n) { t1 <- (1+(i-1)*r)*log((1+(i-1)*r)) t2 <- (i-1)*(1-r)*log(1-r) rri <- ((t1+t2)/i*log(i))-cxn rr <- rri > tol } round(rr,4) } rr1 <- rr(0.5,0.0242) ; rr1

¡Gracias! Espectacular. Me ha servido mucho. El mié., 18 de jul. de 2018 1:15 PM, Víctor Granda García < victorgrandagarcia en gmail.com> escribió: > Hola Sebastián. > > Entiendo que tratas de que aparezca una leyenda con el tipo de curva > (l,o,u,i). Si quieres aprovechar las ventajas de ggplot (como las leyendas > automáticas) normalmente tienes que asignar linetype a una

Hello, I want to find the roots of an equation in two variables. I am aware of the uniroot function, which can do this for a function with a single variable (as I understand it...) but cannot find a function that does this for an equation with more than one variable. I am looking for something implementing similar to a Newton-Raphson algorithm. Thanks. -- Bill Shipley North American Editor for

Full_Name: D Kreil Version: 2.8.1 and 2.9.0 OS: Debian Linux Submission from: (NULL) (141.244.140.179) Group: Accuracy I understand that most floating point numbers are approximated due to their binary storage. On the other hand, I thought that modern math CPUs used guard digits to protect against trivial underflows. Not true? # integers, no problem > 1+1+1==3 [1] TRUE # binary floating

Full_Name: D Kreil Version: 2.8.1 and 2.9.0 OS: Debian Linux Submission from: (NULL) (141.244.140.179) Group: Accuracy I understand that most floating point numbers are approximated due to their binary storage. On the other hand, I thought that modern math CPUs used guard digits to protect against trivial underflows. Not true? # integers, no problem > 1+1+1==3 [1] TRUE # binary floating

Is my understanding correct that the body() function currently can't return a function's body intact, in order, and as characters ready for editing? My testing and reading of body()'s help indicate that it can not. Here's what I'm seeing. Consider pasting 1+ and a function containing x^2 together to get 1+x^2 As you can see below, body() reports three

Buenas tardes, estoy haciendo una gráfica de múltiples lineas pero no he podido generar las legendas. Alguno de ustedes me podría colaborar. library(ggplot2) #### Con b=-2 t=seq (-4, 4, by=0.01) l=exp(t+2)/(1+(exp(t+2))) ##con b igual a -1 t=seq (-4, 4, by=0.01) o=exp(t+1)/(1+(exp(t+1))) ### Con b igual a 0.7 t=seq (-4, 4, by=0.01) i=exp(t-0.7)/(1+(exp(t-0.7))) ### Con b igual a 2 t=seq

Hello. I am trying to do a non-linear fit using the 'nls' command. The data that I'm using is as follows pH k 1 3.79 34.21 2 4.14 25.85 3 4.38 20.45 4 4.57 15.61 5 4.74 12.42 6 4.92 9.64 7 5.11 7.30 8 5.35 5.15 9 5.67 3.24 with a transformation of pH to H <- 10^-pH When using the nls command for a set of parameters - a, b and c, I receive two sets of errors: >

Dear R useRs, I have a problem with nls.lm function of minpackl.lm package. I need to fit the Van Genuchten Model to a set of data of Theta and hydraulic conductivity with nls.lm function of minpack.lm package. For the first fit, the parameter estimates keep changing even after 1000 iterations (Th) and I have a following error message for fit of hydraulic conductivity (k); Reason for