search for: bca

...pulation mean, when should a bootstrap confidence interval be preferred over the elementary t interval? I was hoping the answer would be "always", but some simple simulations suggest that this is incorrect. I simulated some data and calculated 95% elementary t intervals and 95% bootstrap BCA intervals (with the boot package). I calculated the proportion of confidence intervals lying entirely above the true mean, the proportion entirely below the true mean, and the proportion containing the true mean. I used a normal distribution and a t distribution with 3 df. library(boot) samplemean...

...n coefficients for later use so that I can get confidence limits for a whole set of contrasts derived from the coefficients. I'm finding that ordinary bootstrap percentile confidence limits can provide poor coverage for odds ratios for binary logistic models with small N. So I'm exploring BCa confidence intervals. Because the matrix of bootstrapped regression coefficients is generated outside of the boot packages' boot() function, I need to see if it is possible to compute BCa intervals using boot's boot.ci() function after constructing a suitable boot object. The function bel...

I'm confused about name spaces. This morning I installed the boot package because I wanted to look at bca.ci. So I did library(boot), but then I had, > bca.ci Error: Object "bca.ci" not found I had a look in the boot R directory and bca.ci was there as expected. So then I took a look at the NAMESPACE file for the boot package and saw that bca.ci wasn't exported. I tried example(bo...

>From: Jeff Cohen Date: Wed, 26 Jan 2005 19:47:44 -0800 > >Fixed. Yes, now it isn't the path. I've recorded this trace: ------------------------- llvm[3]: Building Debug Bytecode Archive libc.bca /bin/rm -f /C/projects/build/MinGW/llvm-4-1/Debug/lib/libc.bca /C/projects/build/MinGW/llvm-4-1/Debug/bin/llvm-ar rcsf /C/projects/build/MinGW/llvm-4-1/Debug/lib/libc.bca /C/projects/build/MinGW/llvm-4-1/runtime/GCCLibraries/libc/Debug/atox.bc /C/projects/build/MinGW/llvm-4-1/runtime/GCCLibrarie...

Sometimes one might like to obtain pointwise bootstrap bias-corrected, accelerated (BCA) confidence intervals for a large number of statistics computed from a single dataset. For instance, one might like to get (so as to plot graphically) bootstrap confidence bands for the fitted values in a regression model. (Example: Chiu S et al., Early Acceleration of Head Circumference in Child...

...having no problems generating the results, I just need to convert the format of the results such that I can store the results in a dataframe to save out to a database. I am doing the following: ## Generate 20,000 bootstrap samples cod.boot <- boot(trimmed$ratio, cod, R=20000) ## generate 90% BCA boostrap confidence intervals codboot <- boot.ci(cod.boot,conf = c(0.90), type= c("bca")) At this point I have stored the answer I want to the variable codboot, but the problem is it is in the format as follows: BOOTSTRAP CONFIDENCE INTERVAL CALCULATIONS Based on 20000 bootstrap repl...

Dear List, Couple of issues while using functions from ?BCA? library: 1. I am trying to use ?lift.chart? function from ?BCA? library, but facing issues while using model where model formula is passed as formula object in glm. When model formula is written as text, then it works fine. In my case input variables and target variables are going to change dyna...

i was searching for the source of bca.ci, a function of the package boot. I tried require(boot, keep.source=TRUE) but again the source was not viewable. How should i do? Best regards Meinhard Ploner ---------------- PS > version _ platform i386-apple-darwin8.8.1 arch i386 os darwin8...

...tstrap and boot. The former has a function called 'bootstrap' but this does not seem to conform either to the function used in S-plus nor to that described in MASS, 3d ed., p.144. The latter seems to be applicable to the problem I have been asked for help, but I am not happy insofar, as the BCa percentile confidence interval I am getting now is a lot larger. (The data I want to estimate are correlations of 13 data pairs. The lower ci bound went from about 0.16 to 0.03 for the same data set.) Is there a known difference in the use of the wording BCa percentile? -- Dipl.-Math. Wilhelm Ber...

On Thu, 2005-01-27 at 13:16, Henrik Bach wrote: > c:\projects\build\MinGW\llvm-4-1\Debug\bin\llvm-ar.exe: > c:/projects/build/MinGW/llvm-4-1/Debug/lib/libc.bca-000000: Can't destroy > file (hb:2): The process cannot access the file because it is being used by > another process. > make[3]: *** [/C/projects/build/MinGW/llvm-4-1/Debug/lib/libc.bca] Error 2 > ------------------------- > > Like before, the temporary file libc.bca-00000...

Could someone help me on how to correctly try to correct this error message arning : BCa Intervals used Extreme Quantiles Some BCa intervals may be unstable Warning message: Extreme Order Statistics used as Endpoints in: norm.inter(t, adj.alpha) Regards IF [[alternative HTML version deleted]]

Dear All, I am trying to use the bca.ci function on a boot.out object which consists a few NaN's and I want to ignore those NaN's, and get a ci only for the "normal" values. boot.out$t has R number of values for 3000 different statistics, so when I use boot.ci(boot.out, index=i) and i happens to be a column in boot....

Dear List I have run into some problems with boot.ci from package boot. When I try to obtain a confidence interval of type bca, boot.ci() returns the following error when the data set i large: Error in bca.ci(boot.out, conf, index[1L], L = L, t = t.o, t0 = t0.o, : estimated adjustment 'a' is NA Below is an example that produces the above mentioned error on my machine. library(boot) #The wrapper function: w.mea...

...it is being used by another process.' The file is destoyed anyway. I think that the the real error is the path for the file (*/\file.tmp). However, I can't find the bug in the source. Do you have any clue?: ----------------------------- llvm[3]: Building Debug Bytecode Archive libcrtend.bca /bin/rm -f /C/projects/build/MinGW/llvm-4-1/Debug/lib/libcrtend.bca /C/projects/build/MinGW/llvm-4-1/Debug/bin/llvm-ar rcsf /C/projects/build/MinGW/llvm-4-1/Debug/lib/libcrtend.bca /C/projects/build/MinGW/llvm-4-1/runtime/GCCLibraries/crtend/Debug/comp_genericeh.bc /C/projects/build/MinGW/llvm-4...

Hello everybody, when I create an object of class boot with the function tsboot() from the package boot and try to compute several types of confidence intervals with boot.ci("object of class boot created with tsboot") I obtain the warning message, that "BCa-intervals are not defined for time-series bootstraps". Does that hold in general? Or is it just not defined in boot.ci(), because I saw several applications of the BCa-methodology in the time-series context in the literature? So maybe someone can end my confusion and give me an advice, if th...

In the boot package,consider a scalar function to boot. > estimator <- function(x, d) { + mean(x[d]) + } > > data <- city$u > b <- boot(data, estimator, R=1000) > b$t0 [1] 64 > ci <- boot.ci(b, type=c("bca"), conf=.95) > ci$bca conf [1,] 0.95 49.44 991.39 36.78807 110.0254 Now if I want estimators to return a vector,E.g. it's {c(mean(x[d]), sd(x[d]))}, boot.ci() should give me a vector of low bounds and high bounds of the 95% confidence interval. But that does not happen. > esti...

Hi I'm using boot package for some analysis on linear regression coeficients. My problem is that I can not compute bca intervals, I get an error message > bca.ci(blm8901,index=1) Error in if (!all(rk > 1 & rk < R)) warning("Extreme Order Statistics used as Endpoints") : missing value where logical needed The problem is the empinf.reg function that is returning Na when performing a...

Dear R-Experts, Thanks to Prof. Bonnett, I have got an R script working to calculate confidence intervals around the semipartial correlation coefficients. Now, I would like to calculate BCa bootstrap CIs using the boot library and the boot.ci(results, type="all") function. How could I modify my R script (here below reproducible example) to get the BCa bootstrap CIs ? CIsemipartcorr <- function(alpha, part, mult, n) { # Computes a confidence interval for a semipartial c...

...or used in conjunction with RStatFctn. Any help you can offer is appreciated. Thanks, Paul library(boot) RStatFctn <- function(x,d) {return(mean(x[d]))} b.basic = matrix(data=NA, nrow=1000, ncol=2) b.normal = matrix(data=NA, nrow=1000, ncol=2) b.percent =matrix(data=NA, nrow=1000, ncol=2) b.bca =matrix(data=NA, nrow=1000, ncol=2) for(i in 1:1000){ rnormdat = rnorm(30,0,1) b <- boot(rnormdat, RStatFctn, R = 1000) b.ci=boot.ci(b, conf =0.95,type=c("basic","norm","perc","bca")) b.basic[i,] = b.ci$basic[,4:5] b.normal[i,] = b.ci$normal[,2:3] b.perce...

Hi I'm computing a bca interval using bca.ci from the boot package. When I try to use this I get an error > library(boot) > boot(logglm.data,boot.fishpower,2500,coef.vec=coeflm.vec)->blm8901 > bca.ci(blm8901,index=29) Error: cannot allocate vector of size 456729 Kb However my machine has 2GB of memory an...