Displaying 20 results from an estimated 2000 matches similar to: "Skewness test"
2004 Oct 27
2
Skewness and Kurtosis
Hi,
in which R-package I could find skewness and kurtosis
measures for a distribution?
I built some functions:
gamma1<-function(x)
{
m=mean(x)
n=length(x)
s=sqrt(var(x))
m3=sum((x-m)^3)/n
g1=m3/(s^3)
return(g1)
}
skewness<-function(x)
{
m=mean(x)
me=median(x)
s=sqrt(var(x))
sk=(m-me)/s
return(sk)
}
bowley<-function(x)
{
q<-as.vector(quantile(x,prob=c(.25,.50,.75)))
2005 Feb 10
2
testing slopes different than a given value
In a multiple linear regression with two independent
variables is there any function in R to test for the
coefficients being different than some given values?
Example:
x1<-rnorm(100)
x2<-rnorm(100)
y<-3+0.6*x1+0.3*x2
lm(y~x1+x2)
Obtain a test for the coefficients for x1 being
different than 0.6 and for x2 different than 0.3
Thanks
Manuel
2005 Oct 27
1
Box.test
Does p-value on Box.test(data,lag=l) returns probability, that
H0: cor(1)=cor(2)=..=cor(l)=0 holds?
Thanks.
[[alternative HTML version deleted]]
2004 Sep 23
6
detection of outliers
Hi,
this is both a statistical and a R question...
what would the best way / test to detect an outlier value among a series of 10 to 30 values ? for instance if we have the following dataset: 10,11,12,15,20,22,25,30,500 I d like to have a way to identify the last data as an outlier (only one direction). One way would be to calculate abs(mean - median) and if elevated (to what extent ?) delete the
2005 Jan 13
2
multivariate diagnostics
Hi, there.
I have two questions about the diagnostics in multivarite statistics.
1. Is there any diagnostics tool to check if a multivariate sample is from
multivariate normal distribution? If there is one, is there any function
doing it in R?
2. Is there any function of testing if two multivariate distribution are
same, i.e. the multivariate extension of Kolomogrov-Smirnov test?
Thanks for
2005 Jan 28
3
GLM fitting
DeaR R-useRs,
I'm trying to fit a logist model with these data:
> dati
y x
1 1 37
2 1 35
3 1 33
4 1 40
5 1 45
6 1 41
7 1 42
8 0 20
9 0 21
10 0 25
11 0 27
12 0 29
13 0 18
I use glm(), having this output:
> g<-glm(y~x,family=binomial,data=dati)
Warning messages:
1: Algorithm did not converge in: glm.fit(x = X, y =
Y, weights = weights, start = start, etastart =
2008 Jul 12
5
shapiro wilk normality test
Hi everybody,
somehow i dont get the shapiro wilk test for normality. i just can?t
find what the H0 is .
i tried :
shapiro.test(rnorm(5000))
Shapiro-Wilk normality test
data: rnorm(5000)
W = 0.9997, p-value = 0.6205
If normality is the H0, the test says it?s probably not normal, doesn
?t it ?
5000 is the biggest n allowed by the test...
are there any other test ? ( i know qqnorm
2004 Nov 17
1
R: log-normal distribution and shapiro test
Hi,
from what you're writing:
"The logaritmic transformation
"shapiro.test(log10(y))" says: W=0.9773, p-value=
2.512e-05." it seems the log-values are not
distributed normally and so original data are not
distributed like a log-normal: the p-value is
extremally small!
Other tests for normality are available in package:
nortest
compare the log-transformation of your ecdf
2004 Oct 22
3
Convert a list in a dataframe
Hi,
I've a list containing parameters (intercepts &
coefficients) of 12 regressions fitted
> coeff
[[1]]
(Intercept) anno
-427017.1740 217.0588
[[2]]
(Intercept) anno
-39625.82146 21.78025
.....
[[12]]
(Intercept) anno
257605.0343 -129.7646
I want create a data frame with two columns (intercept
and anno)using data in these list.
Any help
2004 Aug 09
2
Using R "boxplot" function in Excel
Hi, I have downloaded the "R-Com and I was able to run "Interactive Graphics
Demo 2" in excel. However, I couldn't create my own boxplot. Whenever I
tried to run any code, it always say" Error in loading DLL", even
"=rput(A1,A2:A20)". Any idea about what's going wrong? A detailed
explaination about how to use R-Excel tool would be greatly appreciated.
2004 Sep 22
5
t test problem?
Hello,
I got two sets of data
x=(124738, 128233, 85901, 33806, ...)
y=(25292, 21877, 45498, 63973, ....)
When I did a t test, I got two tail p-value = 0.117, which is not significantly different.
If I changed x, y to log scale, and re-do the t test, I got two tail p-value = 0.042, which is significantly different.
Now I got confused which one is correct. Any help would be very appreciated.
2004 Jul 07
7
Importing an Excel file
Hello, R users,
I am a very beginner of R and tried read.csv to import an excel file after
saving an excel file as csv. But it added alternating rows of fictitious NA
values after row number 16. When I applied read.delim, there were trailing
several commas at the end of each row after row number 16 instead of NA
values. Appreciate your help.
Kyong
[[alternative HTML version deleted]]
2004 Nov 24
3
T-test syntax question
Hi.
I'd like to do a t-test to compare the Delta values of items with Crit=1
with Delta values of items with Crit=0. What is the t.test syntax?
It should produce a result like this below (I can't get in touch with the
person who originally did this for me)
Welch Two Sample t-test
data: t1$Delta by Crit
t = -3.4105, df = 8.674, p-value = 0.008173 alternative hypothesis: true
2005 Jan 11
3
Kolmogorov-Smirnof test for lognormal distribution with estimated parameters
Hello all,
Would somebody be kind enough to show me how to do a KS test in R for a
lognormal distribution with ESTIMATED parameters. The R function
ks.test()says "the parameters specified must be prespecified and not
estimated from the data" Is there a way to correct this when one uses
estimated data?
Regards,
Kwabena.
--------------------------------------------
Kwabena Adusei-Poku
2004 Jul 21
2
Testing autocorrelation & heteroskedasticity of residuals in ts
Hi,
I'm dealing with time series. I usually use stl() to
estimate trend, stagionality and residuals. I test for
normality of residuals using shapiro.test(), but I
can't test for autocorrelation and heteroskedasticity.
Is there a way to perform Durbin-Watson test and
Breusch-Pagan test (or other simalar tests) for time
series?
I find dwtest() and bptest() in the package lmtest,
but it
2003 Apr 24
5
Fast R implementation of Gini mean difference
I have written the following function to calculate the weighted mean
difference for univariate data (see
http://www.xycoon.com/gini_mean_difference.htm for a related
formula). Unsurprisingly, the function is slow (compared to sd or mad)
for long vectors. I wonder if there's a way to make the function
faster, short of creating an external C function. Thanks very much
for your advice.
gmd
2004 Nov 22
1
R: simulation of Gumbel copulas
Hi,
I found this document, but it concerns S+. If it could
interest you'll see:
http://faculty.washington.edu/ezivot/book/QuanCopula.pdf
Cordially
Vito
You wrote:
Dear R:
Is there a function or a reference to simulate Gumbel
copulas, please?
Thanks in advance!
Sincerely,
Erin Hodgess
mailto: hodgess at gator.uhd.edu
R version 2.0.1 windows
=====
Diventare costruttori di soluzioni
2008 Sep 23
3
Generating series of distributions with the same skewness and different kurtosis or with same kurtosis and different skewness?
Dear R users,
I hope to explain the concepts of skewness and kurtosis by generating
series of distributions with same skewness and different kurtosis or with
same kurtosis and different skewness, but it seems that i cannot find the
right functions.
I have searched the mailing list, but no answers were found.
Is it possible to do that in R? Which function could be used?
Thanks a lot.
--
2005 Jan 25
1
spearman rank test correlation
Hallo,
does anybody know if there is an implementation of the Spearman rank
correlation in R that gives a correct (or at least 'safe') p-value in
the case of ties??
I have browsed the R-help archives but I found nothing.
Thanks a lot in advance for any help,
Antonino Casile
2004 Nov 18
2
Informix database
We use Informix database. I was able to connect to the database with
S-PLUS by using its CONNECT/Java through the JDBC driver.
How can I connect to Informix with R, wither using JDBC or any other
method? we run Linux so I prefer a method other than ODBC.
Thankx for the help