similar to: pwr.2p2n.test when the ratio of n1/n2 is known

Hi, I am trying to sort out a discrepancy between power calculations results between me and another statistician. I use R but I am not sure what she uses. It is on the proportions test and so I have been using pwr.prop.test. I think I have tracked the problem down to pwr.prop.test not using the continuity correction for the test (I did this by using the java applet from

I'm having trouble creating a looping variable and i can't see wher ethe problem arises from any hep gratfully appreciated First create a table x<-table(SURVEY$n_0,exposed) > x exposed False True Under 16 24 1 16-19 68 9 20-24 190 37 25-34 555 204 35-44 330 87 45-54 198 65 55-64 67 35 65+

Hi all, I'm having trouble getting access to the pwr. This is on Ubuntu Lucid Lynx, 64 bit. I'm installing pwr via packages.install('pwr'), and loading it via library(pwr), both of which appear successful. Strangely, I never get access to the pwr object in R. I tried installing it to /usr/local/lib/R/site-library and ~/R/x86_64-pc-linux-gnu-library. I also tried installing it

Hello, I would like to reshape my data for presentation purposes from something like this: > test <- data.frame(a=c("A","A","A","A","B","B","B"),b=c(1,1,2,2,1,1,1),c=1:7) > test a b c 1 A 1 1 2 A 1 2 3 A 2 3 4 A 2 4 5 B 1 5 6 B 1 6 7 B 1 7 to something like this: a b c 1 A 1 1,2 3 A 2 3,4 5 B 1 5,6,7 This seems

Hi, I am trying to produce a plot with an xlabel that reads (x >= 5%) with the >= turned into the correct epression. I can do this up to the percentage sign by specifiing xlab=expression(x>=5). Whatever I do to include the % sign as well doesn't seem to work. xlab=bquote(x>=5.("%")) almost works but includes brackets. Anyonw know how to solve this one Dan PS I am

Hello, I would like to scrape some html tables from a web page and convert them to a data.frame so I can perform further analysis. Could anyone tell me the best way to do this? Would it be more appropriate to use an external tool first? Thanks Dan -- ************************************************************** Daniel Brewer, Ph.D. Institute of Cancer Research Molecular Carcinogenesis

Hello, I have a data.frame like this: a 1,2,3,4 b1 b 6,7 b3 And I would like to transform it to this: a 1 b1 a 2 b1 a 3 b1 a 4 b1 b 6 b3 b 7 b3 I have been looking at ddply but can't seem to work it out. ANy help would be gratefully received. Dan -- ************************************************************** Daniel Brewer, Ph.D. Institute of Cancer Research Molecular Carcinogenesis

Hello, I have a data.frame which I would like to sort with the primary key decreasing while the secondry key is increasing e.g. x <- data.frame(One=c(1,1,1,2,2,3,4,5),Two=c(2,3,1,2,3,3,3,3)) I would like to order it so it looks like this: One Two 8 5 3 7 4 3 6 3 3 4 2 2 5 2 3 3 1 1 1 1 2 2 1 3 i.e. primarily decreasing in the 1st column but if there is a

Hi All, I have a table based on ordial data and i want to compare proportions and i've seen in the pwr package i can use power.prop.test however i want to find out what the sig. value is based on n1,n2,p1,p2 and this package doesn't contain this.. Does anyone know of a package that does or is it a case of writting a function specifically for this? Many thanks in advance [[alternative

Hello, I have a gene expression matrix with columns being samples and rows being genes. I would like to display the expression values for each gene. I have two groups which I colour differently. The aim is to see if there is any difference between the two groups consistently across genes. So the following works well:

Hello, I would like to calculate the 95% confidence intervals for the estimates of a linear model and I just wanted to check that I am doing it correct. Is it just: Estimate + 1.95996*Std.Error to Estimate - 1.95996*Std.Error or is there another approach that doesn't assume a normal distrbution? Thanks. Apologies for my naiivity Dan --

Hello, I am finding that the melt function from the reshape library causes errors when applied to a data.frame that contains numeric and character columns. For example, melt(id.vars="ID",data.frame(ID=1:3,date=c("a","b","c"),value=c(1,4,5))) ID variable value 1 1 date a 2 2 date b 3 3 date c 4 1 value <NA> 5 2

Hi, I have a script that takes a subset of genes on a microarray and tries to fit a coxph model to the expression values for each gene. This seems to work fine but in some cases it produces warnings and/or errors. For example: Error in fitter(X, Y, strats, offset, init, control, weights = weights, : NA/NaN/Inf in foreign function call (arg 6) In addition: Warning message: In fitter(X, Y,

Dear all, For a population of about 200 I have a continuous variable and an ordinal variable. The question I would like to ask is whether the continuously increases (or decreases) as the rank of the ordinal variable increases. I was thinking that a Spearmen's rank correlation or or a chi squared trend might be appropriate. I don't have any experience dealing with ordinal variables so I

Hi, I have a particular barplot I would like to generate, but I am having trouble getting it to work. What I would like is in effect two barplots with stacked bars merged into one. For example, I have two samples (yoda1,yoda2) on which I measure whether two variables (var1,var2) are present or absent for a number of measurements on that sample. > var1 <- data.frame(yoda1=c(3,7),

Hello, I would like to test some data to see whether it has the shape of a step function (i.e. y1 up until x_th and then y2 where x_th is the threshold). The threshold x_th is unknown and the x values can only take discrete values (0,1,2,3,4). An example would be: data<- data.frame(x=1:20,y=c(rnorm(10),rnorm(10,10))) I was thinking along the lines of fitting some sort of piiecewise linear

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

Hello, I am getting a GPG error with the ubuntu repository at the bristol UK mirror. When my source.list has this line: deb http://www.stats.bris.ac.uk/R/bin/linux/ubuntu/ intrepid/ On an "apt-get update" you get this: W: GPG error: http://www.stats.bris.ac.uk intrepid/ Release: The following signatures were invalid: BADSIG D67FC6EAE2A11821 Vincent Goulet <vincent.goulet at

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

I have a script that sometimes produces the following error: Error in assign(".target", method at target, envir = envir) : formal argument "envir" matched by multiple actual arguments Do you think this is a memory issue? I don't know what else it could be as it doesn't always occur even if the script is run with exactly the same data. Does rm() actually free up