Displaying 20 results from an estimated 700 matches similar to: "Problem with code for bootstrapping chi square test with count data"
2007 Nov 27
1
Difference between AIC in GLM and GLS - not an R question
Hi,
I have fitted a model using a glm() approach and using a gls() approach
(but without correcting for spatially autocorrelated errors). I have
noticed that although these models are the same (as they should be), the
AIC value differs between glm() and gls(). Can anyone tell me why they
differ?
Thanks,
Geertje
~~~~
Geertje van der Heijden
PhD student
Tropical Ecology
School of Geography
2007 Sep 04
1
Robust linear models and unequal variance
Hi all,
I have probably a basic question, but I can't seem to find the answer in
the literature or in the R-archives.
I would like to do a robust ANCOVA (using either rlm or lmRob of the
MASS and robust packages) - my response variable deviates slightly from
normal and I have some "outliers". The data consist of 2 factor
variables and 3-5 covariates (fdepending on the model).
2007 Oct 22
3
Spatial autocorrelation
Hi,
I have collected data on trees from 5 forest plots located within the
same landscape. Data within the plots are spatially autocorrelated
(calculated using Moran's I). I would like to do a ANCOVA type of
analysis combining these five plots, but the assumption that there is no
autocorrelation in the residuals is obviously violated. Does anyone have
any ideas how to incorporate these spatial
2007 Nov 16
1
Question about lmRob
Hi,
I am trying to fit a ANCOVA model using lmRob. The P-values of the
variables in the model differ hugely between the summary() function and
the anova() function (from >0.8 in the summary to <0.001in the anova for
the same variable). I understand that with an ANCOVA the order in which
the variables are added to the model matters and that this influences
the P-value, but can this make such
2007 Oct 26
1
Help needed on calculation of Moran's I
Hi,
I am trying to calculate Moran's I test for the residuals for a
regression equation, but I have trouble converting my coordinates into
nb format.
I have used the dnearneigh() funtion now with an arbitrarily high upper
distance to make it include all plots. However, when I do the
lm.morantest() I get a Moran's I value which is the same as the expected
value and a P-value of 1.
I
2010 Jan 21
1
Estimation of S.E. based on bootstrapping (functions with two or more arguments)
Hi all,
I need to estimate S.E. of a certain indicator. The function to compute the
value of indicator contains two arguments. Can anybody tell me how to do it?
Example:
We have data:
a <- c(1:10)
b <- c(11:20)
data <- data.frame(a, b)
Function to compute value of the indicator:
indicator <- function(X, Y) sum(X)/(sum(Y)*2)
Next I need to do the
2019 Jan 13
2
Cómo replicar unos clusters según sistema anterior.
Puede que no me haya expresado certeramente. Es lo que pasa al tocar de
oído.
Tengo unos datos (df) de los que se alguien calculó unas distancias
(dis.df) de las que se hicieron/hacen unos clusters (plot.clus.dis.df).
Todo esto usando un programa on line al que no tengo acceso para ver cómo
hace los cálculos.
Yo tengo los datos, y el programa también me da la matriz de distancias.
Quiero,
2007 Feb 21
1
Chi-Square test
Hello all,
I am doing a Likelihood Ratio (LR) test in my simulation and I have a vector
LR values (each with 1 degree of freedom) at the end of my simulation.
Can anybody tell me how I can write a 'R' code which gives me the p-value
for each of those LR values.
Thanks
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2009 Nov 05
1
partitioning chi-square statistic (g squared)
hi all -
is there a package or library that contains a function for partitioning the
chi-square statistic of an I X J contingency table into its respective
independent parts?
i looked around for this, but i didn't find anything. perhaps there's
another name for this sort of analysis? i know it as "g-squared".
thanks,
chris.
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2007 Jun 26
0
Scale-Inverse Chi square Distribution
Dear all,
sorry to bother you but I was looking for the "scale Inverse Chi square distribution" and I could not find it!
If I remember well , when X~Scale-Inv-Chi-Square (a,b) then X~Inv-Gamma(a/2,a*b/2) but with the shape, scale and rate parameters I always get confused!
Any suggestions?
Thanks a lot for your prompt reply.
Best regards,
Giorgio Di Gessa
2004 Sep 27
1
Enright/Chi-square periodogram / periodicity
I am trying to compute the periodicity of a time series.
I would like to know which function in R does it.
Also, how do I plot a Enright / Chi-square periodogram using R ?
( Enright, J.T., 1965, Journal of Theoret. Biol. 8,426-468)
Greatly appreciate your help.
Thanks in advance,
Sukhaswami Malladi
***************************************************************************
The contents
2007 Apr 23
0
chi square problem
Dear all,
I have a problem that I could not solve neither with spss nor with R.
Please, excuse me if it is atrivial question but I did not find any
soultion.
I have the followig practical problem: we a product that has A, B, C
effects (we differentiated about 30) on health and we want to know
whether these effects are associated with its physical properties
2012 Apr 25
1
calculate correlation effect size using contrast analysis for an omnibus Chi-square test statistic
I am looking for an R package with which one can calculate an effect size for a set of contrasts given an omnibus chi-square test statistic (more than 1 degree of freedom). Is there such a package? Presumably, it would implement the procedure (or something like it) described by Roznow and Rosenthal 1996 Psychological Methods 1: 331-340.
many thanks!
Steven Orzack
Fresh Pond Research Institute
2005 Jun 15
1
Chi square convolution?
Hi,
I want to determine the confidence interval on the sum of two sigma's.
Is there an easy way to do this in R? I guess I have to use some sort of
chisquare convolution algorithm???
Thanx,
Roy
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The information contained in this communication and any atta...{{dropped}}
2002 Jan 08
0
chi square and mahalanobis
Hi all.
I am seeking for a statistical suggestion.
My data set comprises 382 measures each having 169 variables. Each measure
is the outcome of a nuclear magnetic resonance experiment, so each of the
169 points has the same unit.
As I want to do some multivariate calibration using these data, I checked
whether some multivariate outliers existed. I calculated Mahalanobis
distances and did a
2004 Mar 10
1
accuracy of chi-square distribution approximations
Hi there,
How accurate is the aproximation R makes to the Chi-Square distribution?
For example, if I run:
> qchisq(1/1000000,6)
[1] 0.03650857
how accurate is 0.0365 compared to the theoretical percentile? What kind
of approximations have been made in the software's algorithm? It woudl be
useful to know since I am working with tiny percentiles such as one
one-millionth and one
2003 Mar 28
0
the chi-square test for trend / Correction
Hi (again),
Please find here a correction of the function I send previously
---------------------------------------------------------
tableChisqMH=function(x)
{
n=sum(x)
G2=(n-1)*(tablepearson(x)$estimate^2)
dll=1
p.value=1-pchisq(G2,dll)
out=list(estimate=G2,dll=dll,p.value=p.value,dim=dim(x),name="Mantel-Haenszel
Chi-square")
return(out)
}
2003 Feb 28
0
chi square
Hi All,
I woul like to ask you a couple of questions on chisq.test.
First, I have 40 flies, 14 males and 26 females and I want to test for an a
priori hypothesis that the sex ratio is 1:1
sex<-c(14,26)
pr<-c(1,1)/2
chisq.test(se, p=pr, correct=TRUE)
Chi-squared test for given probabilities
data: sex
X-squared = 3.6, df = 1, p-value = 0.05778
If my calculations are correct, this is
2005 Jul 10
1
O/T -2 Log Lambda and Chi Square
Hi R People:
Sorry about the off topic question. Does anyone know the reference
for "-2 Log Lambda is approx dist. Chi square", please?
It may be Bartlett, but I'm not sure....
thanks in advance!
Sincerely,
Laura Holt
mailto: holtlaura at gmail.com
2017 Dec 18
0
chi-square distribution table
Please could you tell me how to make code to outpot chi-square
distribution table?
Please help