search for: wilcox_test

Dear R-forumites, I want to apply a Wilcoxon test on subsets of the data frame mydata, splitted using the myindice variable. When I send : wilcoxtest <- by(mydata, mydata$myindice, function(x) {wilcox_test(x$value~x$fact)}) I get : Error in eval(expr, envir, enclos) : object "x" not found whereas wilcoxtest <- by(mydata, mydata$myindice, function(x) {wilcox.test(x$value~x$fact)}) works ! Why does it fail with the wilcox_test only? And, most important, how can I a...

Dear All, I have two simple data samples (no groups or factors, etc.) and would just like to compute the two-sample Wilcoxon Rank Sum test using the wilcox_test function contained in the coin package, which is reportedly better than the regular wilcox.test function because it performs some adjustment for ties. Would anyone know how to craft a script to perform this task? Much appreciated. Janh [[alternative HTML version deleted]]

Hi, I became a little bit confused when working with the Wilcoxon test in R. As far as I understood, there are mainly two versions: 1) wilcox.test{stats}, which is the default and an approximation, especially, when ties are involved 2) wilcox_test{coin}, which does calculate the distribution _exactly_ even, with ties. I have the following scenario: #---BeginCode--- # big example size = 60 big1 = rnorm(size, 0, 1) big2 = rnorm(size, 0.5, 1 g1f = rep(1, size) g2f = rep(2, size) big = c(big1, big2) data_frame = data.frame(big, gr=as.factor(...

Does anyone know why wilcox.exact gives W-statistic 6 instead of 12 as indicated below. 12 is the rank sum of group 0 of x, which is the linear statistic computed by wilcox_test. y<-c(1,2,3,4,5) x<-c(1,1,0,0,0) (a) wilcox.exact wilcox.exact(y~x) Exact Wilcoxon rank sum test data: y by x W = 6, p-value = 0.2 alternative hypothesis: true mu is not equal to 0 (b) wilcox_test tt<-wilcox_test(y~factor(x),distribution="exact") statistic(tt,"line...

Recently, I ran a series of Kruskal-Wallace tests [kruskal.test()] using by() to group by site Output is a list: >Herb.KW Herb.df$ID: 10-1 Kruskal-Wallis rank sum test data: Indicator_Rating by Year Kruskal-Wallis chi-squared = 15.24, df = 7, p-value = 0.03302 ----------------------------------------------------------------------------------------------------- Herb.df$ID: 18-1

I need to perform the Exact Wilcoxon Mann-Whitney on a subset of my database. Assuming that IPPO is my data frame and IPPOBIS is the subset my variable still have 3 different levels and the function wilcox_test (package "coin") does not accept it. I do not know how to overcome this problem. ippo <- c(rep("A",10),rep("B",10),rep("C",10)) ippo2 <- c(rnorm(10,0,1),rnorm(10,10,10),rnorm(10,10,10)) IPPO <- data.frame(ippo,ippo2) IPPOBIS <- IPPO[IPPO$ippo =...

Hi, Two functions wilcox.exact and wilcox_test give slightly different confidence intervals of the difference of the medians: for example y<-c(0,0,1.081,0.594,0,0.769,0,0.009,0,0,0.798,0.405,0.498,0.946,1.35,1.149,0.528) x<-c(rep(1,10),rep(2,7)) aa<-wilcox.exact(y~x,conf.int=TRUE) bb<-wilcox_test(y~factor(x),distribution="e...

Hello, I use t.test for normal distributed and wilcox.test for non-normal distributed samples. It is easy to write a function for t.test that calculates the effect size, because all parts of the formula are available from the t.test result: r = sqrt(t*t / (t*t + df)) However, for Wilcoxon tests, the formula for effect sizes is: r = Z / sqrt(N) I wonder how I can calculate the Z-score in R for

An earlier post had posed the question: "Does anybody know what is relation between 'T' value calculated by 'wilcox_test' function (coin package) and more common 'W' value?" I found the question interesting and ran the commands in R and SPSS. The W reported by R did not seem to correspond to either Mann-Whitney U, Wilcoxon W or the Z which I have more commonly used. Correction for ties may hav...

Hi, I am running the following example which can be found on page 12 of the pdf file of COIN package wt<-wilcox_test(pd~age,data=water_transfer,distribution="exact", conf.int=TRUE) "wt" actually contains the estimate of difference in location and the confidence interval of it. I am just wondering how can I extract these values? From the examples, I understand that the Wilcoxon statistic can...

Dear Sir, I am doing some work on a population of patients. About half of them are admitted into hospital with albumin levels less than 33. The other half have albumin levels greater than 33, so I stratify them into 2 groups, x and y respectively. I suspect that the average length of stay in hospital for the group of patients (x) with albumin levels less than 33 is greater than those

.... While the former entry probably is the result of some stupid algorithmic twist in some software (take your guesses), I think that wilcox_exact in the coin package is superior by not assuming that data are to be tied when deemed close enough by some poor defined measure (but I'm biased). Try wilcox_test(delta_hba1c~as.factor(Treatment), data=U, distribution="exact") And wilcox_test(signif(delta_hba1c,3)~as.factor(Treatment), data=U, distribution="exact") Thanks to Torsten Hothorn for discussing this with me and for producing such a neat package (together with Kurt Hornik, Mark...

Hello, I'm having some issues grouping cases for some Mann-Whitney U tests I'm attempting to run. I'm willing to use wilcox.test if it'll work; I've also tried wilcox_test() from the "coin" package. Here's the deal: for each column (A through H), I would like to run the two-sample independent test, comparing Group 5 (CD8.14 through CD8.17) to Group 6 (CD8.18 through CD8.21). So, for A, test Group 5 agains Group 6, for B, test Group 5 against Group 6, an...

Hello List, I'm trying to prepare some lecture notes on non parametric methods, and I can't manually reproduce the results of the wilcox.test function for ordinal data. The data I'm using are from David Howell's website, available here http://www.uvm.edu/~dhowell/StatPages/More_Stuff/OrdinalChisq/OrdinalChiSq.html If I run the wilcox.test function on the data I get a p-value of

LO HICE DE ESTA MANERA Y FUNCIONÓ a_HTA <- (estudiantes1[,c(1)]) IMC <- (estudiantes1[,c(2)]) estudiantes4 <- data.frame( IMC, a_HTA = factor(c(rep("si", 29), rep("no",30)))) wt <- wilcox_test(IMC ~ a_HTA, data = estudiantes4, distribution = "exact", conf.int = TRUE) print(wt) De: Jorge I Velez [mailto:jorgeivanvelez@gmail.com] Enviado el: Sunday, September 15, 2013 4:37 PM Para: Dr. José A. Betancourt B. CC: R-help-es Asunto: Re: [R-es] b Eso no f...

R 2.1.1 on Windows 2K I hope one and all will allow both an R question and a general stats question: (1) Is there any function that will perform non-parametric tests such as a sign test or a signed rank test? I know I could program both but I would prefer not re-inventing the wheel. (2) When performing a sign test, the usual practice is to drop zero values. Is there any theoretical reason

Hi, I am very confused with constructing the wilcox.test in R. I have two populations 'original' and 'test'. I want to know if the 'test' is generally 'lower' than original. I use alpha of 0.05. So do I write the function as wilcox.test(original, test, alternative="l")? or wlcox.test(original, test, alternative = "g")? or wilcox.test(test,

Dear R friends, here I write again about the wilcox.exact() problem. I want to compare two sets of categorical data, and in one case it says "negative length vectors not allowed", and in the other one I get the error "cannot allocate vector of length ...". On http://rapidshare.com/files/298621893/wilcox.exact_trouble.Rdata.html you can download the data that cause the

Dear Sir, I am comparing two samples using wilcox.test in R. Literature appears to describe mann whitney u test as the most appropriate test to use on my data. is the wilcox.test function equivalent to mann-whitney u? Is there a way to gain the U-value as apposed to the W-value in R? Thank you

...na es asi estudiantes1<-read.csv("estudiantes1.csv",header=TRUE, sep=",", dec=".") a_HTA <- (estudiantes1[,c(1)]) IMC <- (estudiantes1[,c(2)]) estudiantes4 <- data.frame( IMC, a_HTA = factor(c(rep("si", 29), rep("no",30)))) wt <- wilcox_test(IMC ~ a_HTA, data = estudiantes4, distribution = "exact", conf.int = TRUE) print(wt) en la ayuda dice Independent Two- and K-Sample Location Tests Description Testing the equality of the distributions of a numeric response in two or more independent groups against sh...