similar to: Permutation or Bootstrap to obtain p-value for one sample

Dear List Members, I have two small samples (n=20), the distributions are highly skewed. Does it make any sense to do a boostrap test to check for difference in means? And if so, could this be done like this: x <- numeric(10000) for(i in 1:10000) { x[i] <- mean(sample(sample1,replace=TRUE)) - mean(sample(sample2,replace=TRUE)) } (mean(sample1)-mean(sample2))/sd(x) Regards, Erika

Hello, I would like to post the below position on your site. Thanks, Quantitative Analyst/Quantitative Developer MSIM Global Risk & Analysis, Quantitative Research & Model Review group Morgan Stanley Investment Management (MSIM), together with its investment advisory affiliates, has more than 680 investment professionals around the world and approximately $279 billion in assets under

I am trying to calculate monthly means by year of phosphates and nitrates from a multi year data set. Can anybody help me out with the most effective way to do this? My data looks like this: Collection_Date                   Test.Name              Value 2000-01-24 17:00:00            Phosphate               0.108 2000-01-24 17:00:00            Nitrate                     0.037 2001-11-12

I'm having a problem when using heatmap. Even though the diagonal of my matrix is all the same value, the diagonal of my heatmap is not all the same color. Any suggestions? Here is some reproducible code: ######################################### # Get data nba <- read.csv("http://datasets.flowingdata.com/ppg2008.csv", sep=",") # Reorder nba <-

Hi, I have a little problem that puzzles me about contradictory results returned by a bootstraped t-test (as in MASS 3rd ed p. 146) versus a permutation t-test (as in MASS 3rd ed, p 147). Data are measurements done on 100 cells in 9 slides of fish blood. With one method, cells are randomly sampled, and with the other method, the operator selects cells arbitrarily (in a way it is done usually

Dear R experts, I would like to explore if and to what extent bootstrapping and permutation statistics can help me for my research (functional brain imaging). I am looking for an introductory textbook, rather legible. I have statistical knowledge, but I am definitely no statistical or mathematical guru. Do you have suggestions for a useful textbook? Thanks a lot, Peter

Hi, I've been looking at ways to make pyramid plots in R. I like the pyramid.plot method in plotrix as it seems the simplest to use and building them in ggplot looks a bit more code intensive than I'd like, being as I'm new to R. This package does pretty much what I need it to do, however I can't seem to scale the x axis labels. The other labels scale fine with labelcex. I

Hi I am trying to find a parametric bootstrap confidence interval and when I used the boot function I get zero bias and zero st.error? What could be my mistake? Thank you and take care. Laila [[alternative HTML version deleted]]

Hello R users, I wish to draw a type of horizontal bar chart for two groups (males and females). The values for one group will start at the y-axis and point to the left, and the values for the other group will start at the y-axis and point to the right. If you're (un)lucky, the resulting graph can assume the shape of a Christmas tree. The data are left.side <- c(107092, 113053,

I hope this question is adequate for this list I use the nnet code from V&R p. 348: The very nice and general function CVnn2() to choose the number of hidden units and the amount of weight decay by an inner cross-validation- with a slight modification to use it for classification (see below). My data has 2 classes with unequal size: 45 observations for classI and 116 obs. for classII With

Dear list, For educational purposes I have been working with the script below. I have a observation: line 31 #CScal[i] = (amo^2) # IT IS WRONG, I KNOW, BUT IT MAKE R TO CRASHES! I'm thinking this is a possible bug in the R! And I have a couple of doubts: 1) line 51 #curve(dchisq(x, n-1), add = T, col = 'red' I think that it is correct, but the function no

Hi, I have Forecast Class and Observed Class in a data matrix as below. > Sample1 FCT OBS 1 1 5 2 2 4 3 3- 3+ 4 3 3 5 3+ 3- 6 4 2 7 5 1 I want to find the difference between Observed and Forecast Classes. How can I get this done? I tried to following to convert the 1 through 5 classes, to 1 through 7 for both OBS and FCT column. > Sample1$OBS2 <- Sample1$OBS

Hello all, I have what feels like a simple problem, but I can't find an simple answer. Consider this data frame: > x <- data.frame(sample1=c(35,176,182,193,124), sample2=c(198,176,190,23,15), sample3=c(12,154,21,191,156), class=c('a','a','c','b','c')) > x sample1 sample2 sample3 class 1 35 198 12 a 2 176 176

Dear Researchers, I have several files as this example: Myfile_MyArea1_sample1.txt i wish to split in "Myfile", "MyArea1", "sample1", and "txt", becasue i need to use "sample1" label. I try to use "strsplit" but I am able just to split as "Myfile_MyArea1_sample1" and "txt" OR "Myfile", "MyArea1",

Is it possible to query LDAP differently for different protocols? I am using dovecot for both pop3/imap and lmtp deliveries and there are different enable flags in ldap for them. I tried wrapping user_filter inside the protocols in the file dovecot-ldap.conf.ext as shown below but this didn't seem to work. protocol lmtp { user_filter =

Dear experts, Please forgive the puzzled title and the length of this message - I thought it would be best to be as complete as possible and to show the avenues I have explored. I'm trying to fit a linear model to data with a binary dependent variable (i.e. Target.ACC: accuracy of response) using lrm, and thought I would start from the most complex model (of which "sample1.lrm1" is

I am looking for an algorithm (written in R (preferably) or C, but even pseudo-code in a text book maybe fine) to determine the sign of a permutation. What is that? Well, a permutation is either even or odd, the sign is +1 or -1, respectively, see, e.g., http://en.wikipedia.org/wiki/Signature_of_a_permutation which also says >> In practice, in order to determine whether a given

I am wondering why sieve-filter is so slow compared to gnu sieve. I run mpop (like getmail) to download from a pop3 server to a local mbox file: ~/mail/email-incoming-unsorted This step is very fast. The next step, I throw the email-incoming-unsorted mbox file at a sieve processor, to sort the emails from that mbox, into other mboxes, according to the sieve rules file. Up until a couple days

I saw the manual of this function but not sure what to do. I have a array contain 7 numbers and want to choose 4 to do permutation test. But using this function with parameters as onet.permutation(scores,4), it returns 0. Instead, with no parameter, onet.permutation(), it returns something but every time it's different. Please tell me how am I supposed to do it. Thanks a lot -- View this

Hi, Is there any way to find the permutation function of the sorting and to apply the function (or its inverse) elsewhere? For example, the following permutation function from the sorting in the matrix form is c(1,2,3), c(2,1,3) > sort(c("bc","ac","dd")) [1] "ac" "bc" "dd" I try to find it in the permutations/permute