Displaying 20 results from an estimated 30000 matches similar to: "Adding noise"
2010 Oct 22
2
Bayesian constrained regression method?
Hello everyone,
I am trying to estimate the parameter b.
I have Y and X1 which I know and they are both random. However, I also have
X2 which I don't know and is also random. I want to estimat b from the
model:
Y = b*X1 + ( 1 - b ) * X2
Can anyone offer some suggestions. The values of Y and X1 are both pvalues
so they are constrained in (0,1).
--
Thanks,
Jim.
[[alternative HTML version
2010 Jan 10
1
Mixtures of Discrete Uniforms
I want to create the mixture formulation of a discrete uniform ie, say
f(x) = 1/10, for i = 1,2,3,4,5,6,7,8,9 and 10 and
another discrete distribution which has the same values of x, but he
probabilities can vary. Can this be done on any package in R? an if so, can
the package estimate the 'probabilities' of each of the x value as well as
the mixing proportion if I have the data?
2009 Jun 15
1
multcomp: contrasts for count data
Hi,
I would like to derive p-values for pair-wise comparison (Tukey's) of
effects when the response is a count.
I am trying a test case where y ~ Po( lambda(x) ). x has three
levels : A, B and C with lambda(x) = 10, 20 and 20 respectively.
Hence, p-values for the contrast C - B should distribute uniformally.
I have implemented this test case as below but do not get uniform
2011 Jul 22
3
Cox model approximaions (was "comparing SAS and R survival....)
For time scale that are truly discrete Cox proposed the "exact partial
likelihood". I call that the "exact" method and SAS calls it the
"discrete" method. What we compute is precisely the same, however they
use a clever algorithm which is faster. To make things even more
confusing, Prentice introduced an "exact marginal likelihood" which is
not
2011 Jul 07
4
Simulating from the null distribution of a 2 x 3 table
Dear all,
I want to simulate from the null distribution of the following 2 x 3 table,
2 5 10
4 8 5
I am using a chi-squared test.
Anyone has any idea how to do this?
--
Thanks,
Jim.
[[alternative HTML version deleted]]
2013 May 16
2
R looping help
Hey I'm not really sure what I should put on here, but I am having trouble
with my R code. I am trying to get the p-values, R^2s etc for a number of
different groups of variables that are all in one dataset.
This is the code:
#Stand counter
st<-1
#Collections
stands<-numeric(67)
slopes<-numeric(67)
intercepts<-numeric(67)
mses<-numeric(67)
rsquares<-numeric(67)
2012 Feb 09
2
GLM - guess the distribution of the response variable
Dear all,
I have question regarding GLMs:
I have a discrete response variable and a continuous explaining
variable. Like this:
http://www.myimg.de/?img=example1db0f.jpg
I want to use a GLM to investigate. I have to specify the "familiy of
the distribution of the response variable" - or, maybe more precise, the
"family of the distribution of the residuals of the response
2006 Mar 22
4
pbinom( ) function (PR#8700)
Full_Name: Chanseok Park
Version: R 2.2.1
OS: RedHat EL4
Submission from: (NULL) (130.127.112.89)
pbinom(any negative value, size, prob) should be zero.
But I got the following results.
I mean, if a negative value is close to zero, then pbinom() calculate
pbinom(0, size, prob). dbinom() also behaves similarly.
> pbinom( -2.220446e-22, 3,.1)
[1] 0.729
> pbinom( -2.220446e-8, 3,.1)
2006 Jul 28
1
mult comp significance
This has a stats question and a R question. I am sure there are many
core statisticians here how would know the answer to this simple
question. In determining the significant comparisons using the methods
in multcomp, the ones that are designated as significant are the ones
that do not intersect the zero line. What is the physical meaning of
this and why are those considered significant? I can
2011 Apr 08
4
Fast version of Fisher's Exact Test
Is anyone aware of a fast way of doing fisher's exact test for a series of 2
x 2 tables in R? The fisher.test is really slow if n1=1000 and n2 = 1000.
--
Thanks,
Jim.
[[alternative HTML version deleted]]
2008 Jun 20
1
Unexpected Behavior (potentially) in t.test
Greetings,
I have stumbled across some unexpected behavior (potential a bug) in, what I
suspect to be R's (2.6.2 on Ubuntu Linux) t.test function; then again the
problem may exist in my code. I have shutdown R and started it back up,
re-run the code and re-experienced the error. I have searched on Google for
the abnormal termination error message "(stderr < 10 * .Machine$double.eps *
2010 Aug 17
3
Weird differing results when using the Wilcoxon-test
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
2007 Jun 29
1
Shapiro Test P Value Incorrect? (PR#9768)
Full_Name: Jason Polak
Version: R version 2.5.0 (2007-04-23)
OS: Xubuntu 7.04
Submission from: (NULL) (137.122.144.35)
Dear R group,
I have noticed a strange anomaly with the shapiro.test() function. Unfortunately
I do not know how to calculate the shapiro test P values manually so I don't
know if this is an actual bug.
So, to produce the results, run the following code:
pvalues = 0;
for
2011 Aug 23
2
qnorm?
Hi everyone,
I have the following problem. I have some small p-values but when I use
qnorm(1-4e-30)
I get an error.
Is there anyway to get around this?
--
Thanks,
Jim.
[[alternative HTML version deleted]]
2013 Jan 09
1
t-test behavior given that the null hypothesis is true
Dear all,
I observer a strange behavior of the pvalues of the t-test under the null
hypothesis. Specifically, I obtain 2 samples of 3 individuals each from a
normal distribution of mean 0 and variance 1. Then, I calculate the pvalue
using the t-test (var.equal=TRUE, samples are independent). When I make a
histogram of pvalues I see that consistently the bin of the smallest
pvalues has a lower
2001 Feb 06
2
barplots with pictex
Dear R People,
I want to include a barplot corresponding to a simple discrete probability
distribution in a LaTeX document. I decided to use the pictex
driver. After a certain amount of messing about, I came up the stuff
below. It does not look too bad, however, there is one very obvious piece
of weirdness, ie. the y axis terminates at 0.1 and does not extend down
further. I tried to adjust this
2013 Mar 02
3
print method like print.anova()
I have a print method for a set of statistical tests, vcdExtra::CMHtest,
for which I'd like to
have more sensible printing of pvalues, as in print.anova().
[Testing this requires the latest version of vcdExtra, from R-Forge
**|install.packages("vcdExtra", repos="http://R-Forge.R-project.org")|**
]
With my current print method, I get results like this, but all Prob
values
2011 Jul 04
2
clustering based on most significant pvalues does not separate the groups!
Hi all,
I have some microarray data on 40 samples that fall into two groups. I have
a value for 480k probes for each of those samples. I performed a t test
(rowttests) on each row(giving the indices of the columns for each group)
then used p.adjust() to adjust the pvalues for the number of tests
performed. I then selected only the probes with adj-p.value<=0.05. I end up
with roughly 2000
2008 Jan 19
1
How do we get two-tailed p-values for rlm?
How do we get 2-tailed p-values for the rlm summary?
I'm using the following:
> fit <- rlm(oatRT ~ oatoacData$erp, psi=psi.bisquare, maxit=100,
na.action='na.omit')
> fitsum <- summary(fit, cor=F)
> print(fitsum)
Call: rlm(formula = oatRT ~ oatoacData$erp, psi = psi.bisquare, maxit = 100,
na.action = "na.omit")
Residuals:
Min 1Q Median
2017 Jun 29
0
Help : glm p-values for a factor predictor
It might help if you provided the code you used. It's possible that
you didn't use direction="backward" in stepAIC(). Or if you did, it
was still running, so whatever else you try will still be slow. The
statement "R provides only the pvalues for each level" is wrong: look
at the anova() function.
Bob
On 29 June 2017 at 11:13, Beno?t PELE <benoit.pele at