Displaying 20 results from an estimated 6000 matches similar to: "help on ks.test and shapiro.test"
2001 Jul 02
2
Shapiro-Wilk test
Hi,
does the shapiro wilk test in R-1.3.0 work correctly? Maybe it does, but can
anybody tell me why the following sample doesn't give "W = 1" and
"p-value = 1":
R> x<-1:9/10;x
[1] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
R> shapiro.test(qnorm(x))
Shapiro-Wilk normality test
data: qnorm(x)
W = 0.9925, p-value = 0.9986
I can't imagine a sample being
2008 Apr 18
1
2.2e-16 a magic number? ks.test help
Hello,
I'm trying to test my data for normality.
I enter the data (95ish species counts)
run >ks.test (data,pnorm)
and get a p- value <2.2e-16
But this seems to be the p-value no matter what the data I enter. (I
have multiple datasets and am testing them all for normality).
[Actually, I just entered a vector of 1's and the p-value changed.]
When I use the >Shapiro.test command,
2012 Apr 04
1
Shapiro-Wilk cpoefficients: 2 Qs
Greetings!
I want to have the coefficients that R uses in shapiro.test()
for the Shapiro-Wilk test for a prticular sample size, i.e.
the a[i] in
W = Sum(a[i]*x[i])/(Sum(x[i] - mean(x))^2)
(where the x[i] are sorted). Two questions:
Q1:
Is there a readymade R function from which I can extract these?
Q2:
I was wondering if I might be able to modify the code for the
function shapiro.test() so
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
2005 Mar 18
1
Pb with ks.test pvalue
Hello,
While doing test of normality under R and SAS, in order to prove the efficiency of R to my company, I notice
that Anderson Darling, Cramer Van Mises and Shapiro-Wilk tests results are quite the same under the two environnements,
but the Kolmogorov-smirnov p-value really is different.
Here is what I do:
> ks.test(w,pnorm,mean(w),sd(w))
One-sample Kolmogorov-Smirnov test
data: w
D
2012 May 02
2
output Shapiro-Wild results to a table
Hello,
I have applied the Shapiro test to a matrix with 26.925 rows of data using the following
F1.norm<-apply(F1.n.mat,1,shapiro.test)
I would now like to view and export a table of the p and W values from the Shapiro test, but I am not sure how to approach this.
I have tried the following with errors.
> write.table(x=F1.norm,file="I:/R_Work/F1/Shapiro.csv",
2006 Jul 12
2
shapiro.test() output
R Users:
My question is probably more about elementary statistics than the
mechanics of using R, but I've been dabbling in R (version 2.2.0) and
used it recently to test some data .
I have a relatively small set of observations (n = 12) of arsenic
concentrations in background groundwater and wanted to test my
assumption of normality. I used the Shapiro-Wilk test (by calling
shapiro.test()
2010 Sep 22
2
kstest vs shapirotest
Dear R-users
Idea:
Analysing tree height frequency with hist(), normal distribution (ks.test & shapiro.test) and skewness (package e1071 - thanks a lot for this useful package)as an indication of possible self-thinning in an experimental tree stand.
Problem:
Results from the ks.test and the shapiro.test are not comparable (see example of both tests). Tree height is a nice continuous
2005 Nov 09
1
Problems with Shapiro Wilk's test of normality.
Hi,
I am trying to create a table with information from Shapiro Wilk's
test of normality.
However, it fails due to lack of sample size, it says, but the way I
see it, this is not a problem.
(See the table of sample sizes (almost) at the bottom).
Applying a different function using a similar ftable call is not a
problem (See the bottom table).
This is R 2.1.0 on Linux (Gentoo).
/Fredrik
2010 May 26
3
shapiro.test
Hi,
I am not so sure about an error note I got when using shapiro.test.
I imported some data into R by wrinting it into a .txt file via
> tab1<-read.table("etc....txt",header=T)
> attach(tab1)
The following object(s) are masked _by_ .GlobalEnv :
ozon
> ozon$V1 [1] 2.5 3.0 5.6 4.7 6.5 6.7 1.7 5.3 4.6 7.4 5.4 4.1 5.1 5.6 5.4 6.1 7.6[18] 6.2 6.0 5.5 5.8 8.2 3.1 5.8 2.6
Now
2013 Apr 05
2
How to perform a grouped shapiro wilk test on dataframe
Hello,
I was wandering if it is possible to perform on a dataframe called 'all' a
shapiro wilk normality test for COUNTS by variable Group
ACTIVITY? Could it be done using plyer? I saw an eg that applies to an
array but not to a dataframe:
lapply(split(dataset1$Height,dataset1$Group),shapiro.test)
Any thoughts would be much appreciated.
My dataframe is in shape:
dat ACTIVIT
2008 Nov 21
1
question about shapiro.test()
Hi all!
I tried to perform Shapiro-Wilk test for my sample of 243 values.
> Us
[1] -10.4 -13.1 -12.2 38.1 -18.8 -13.3 -11.7 29.3 49.7 6.8 12.7 16.3
[13] 5.8 -0.7 -29.4 4.1 38.8 -1.4 8.8 15.6 32.9 -5.3 19.1 35.8
[25] 4.0 -1.5 0.6 -4.2 -10.0 -4.0 1.1 48.9 -21.0 -5.3 5.8 -10.8
[37] 21.9 8.2 -3.2 -3.9 -2.3 12.6 -4.7 -8.0 11.8 27.4 -9.5 -20.8
[49]
2009 Feb 06
1
beanplot, Error in shapiro.test(x)
Dear all,
I am trying to create beanplots from a dataset for which boxplot works fine.
(MACOS, R 2.8.1 GUI 1.27 Tiger build 32-bit (5301))
I am getting the following error message:
Error in shapiro.test(x) : sample size must be between 3 and 5000
I am not even sure why the shapiro.test is being used, but is there any
workaround ?
Thanks !
Markus
[[alternative HTML version deleted]]
2000 Sep 25
1
Interpretation of Shapiro-Wilk
Can anybody tell me the exact meaning of the $statistic and $p.value
calculated by shapiro.test? Unfortunately it is not covered in my few
text books, and I cannot find the explanation in the R documentatiom or
on-line.
If I have a test statistic, T, which is Normally distributed with mean=m
and sd=s under the null hypothesis, then I can convert T to a p-value
(one-sided) using:
p <- pnorm(T,
2007 Sep 29
1
Shapiro-Welch W value interpretation
Hello,
I have tested a distribution for normality using the Shapiro-Welch
statistic. The result of this is the following:
Shapiro-Wilk normality test
data: mydata
W = 0.9989, p-value = 0.8791
I know that the p-value > 0.05 (for my purposes) means that the data
IS normally distributed but what I am not sure is with the W value,
what values tell me that the data is normally
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
2003 Feb 10
2
shapiro.test
Hi
The shapiro.test function outputs a value of the W statistic, which
should be 1 if the distribution is normal, and a p-value for the test
(as the documentation states).
I'm a bit confused with some results. I'm getting a W=0.9977 and a
p-value=0.1889.
I was expecting that a W of 0.9977 would tell me that the distribution
is normal so p-value should be small ...
What am I missing ?
2011 Sep 30
3
error while using shapiro.test()
hey all, I'm just getting used to R and i'm having issues when it comes to
reading my data in rows rather than columns. any good advice would be much
appreciated !
here is the error:
> data1 <- read.table(file.choose(),header=T)
> x1 <- c(data1[1,1:5])
> shapiro.test(x1)
Error in sort.int(x, na.last = na.last, decreasing = decreasing, ...) :
'x' must be atomic
2003 Mar 28
2
file.show("morley.tab") responds "NO FILE"
"An Introduction to R", Venables and Smith, Version 1.6.2 (2003-01-10)
http://cran.r-project.org/doc/manuals/R-intro.pdf
has in its "Appendix A: A sample session", page 81,
file.show("morley.tab")
I get the response
NO FILE morley.tab
The following "Introduction to the R Project for Statistical Computing"
www.itc.nl/~rossiter/teach/sstat14/
2008 Oct 09
1
interpreting Shapiro-Wilks test result
Hi all,
I am newbie in using R software and also doing statistical test. I want to know if my data in in normal distribution. I have 2 groups of data and I did calculate Shapiro Wilks using R software. Here is the results:
Group 1: W = 0.9206, p-value = 0.01683
Group 2: W = 0.9626, p-value = 0.4694
I am not quite sure what default confidence level (CF) is used in calculating Shapiro Wilks.