Displaying 20 results from an estimated 2000 matches similar to: "Looking for a test of standard normality"
2011 Jun 07
1
extract data features from subsets
I have a large dataset similar to this:
ID time result
A 1 5
A 2 2
A 3 1
A 4 1
A 5 1
A 6 2
A 7 3
A 8 4
B 1 3
B 2 2
B 3 4
B 4 6
B 5 8
I need to extract a number of features for each individual in it (identified by "ID"). These are:
* The lowest result (the nadir)
* The time of the nadir - but if the nadir level is present at >1 time point, I need the minimum and maximum time of nadir
2007 Apr 23
1
data recoding problem
Hi R experts,
I have a data recoding problem I cant get my head around - I am not that
great at the subsetting syntax. I have a dataset of longitudinal
toxicity data (for multistate modelling) for which I want to also want
to do a simple Kaplan-Meier curve of the time to first toxic event.
The data for 2 cases presently looks like this (one with an event, the
other without), with id representing
2001 May 28
3
normality test
Hello
I have used recently the kolmogorov smirnov test,
which is a test of normality.
This test is named ks.test() in ctest library of R.
I wonder if the results of ks.test () are true, because
the results are strange, time to time.
thank you for help
meriema
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2011 Apr 26
3
Normality tests
I have a large amount of data which I break down into a collection of
vectors of 100-125 values each. I would like to test the normality of the
vectors and compare them. In the interactive mode I can test any one vector
using the Shapiro-Wilk test or the Kolmogorov-Smirnov test. My problem is
that when I try to write out the results to a file, the term output is a
mixture of alpha characters
2007 Feb 26
2
how to fill between 2 stair plots
Hi all,
I want to create a simple plot with 2 type='s' lines on it:
plot(a, b, type='s')
lines(x, y, type='s')
I wish to then fill the area between the curves with a colour to
accentuate the differences eg col=gray(0.95). I cant seem to come up
with a simple method for this. Any pointers in the right direction much
appreciated.
Cheers
Scott
2010 Jun 23
2
About normality tests...
Hi all,
I have two very large samples of data (10000+ data points) and would
like to perform normality tests on it. I know that p < .05 means that
a data set is considered as not normal with any of the two tests. I am
also aware that large samples tend to lead more likely to normal
results (Andy Field, 2005).
I have a few questions to ensure that I am using them right.
1) The Shapiro-Wilk
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
2005 Sep 09
2
test for exponential,lognormal and gammadistribution
hello!
i don't want to test my sample data for normality, but exponential- lognormal-
or gammadistribution.
as i've learnt the anderson-darling-test in R is only for normality and i am
not supposed to use the kolmogorov-smirnov test of R for parameter estimates
from sample data, is that true?
can you help me, how to do this anyway!
thank you very much!
nadja
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
2008 Jan 29
1
Help needed on Normality test
Hi all T gurus,
I would like to test if my dataset is indeed from N(0, 0.011908969).
K.S. test gives following result:
> ks.test(data, "pnorm", 0, 0.011908969)
One-sample Kolmogorov-Smirnov test
data: data
D = 0.1092, p-value = 1.318e-05
alternative hypothesis: two-sided
How ever "Shapiro-Wilk" test give following :
>
2007 Feb 15
1
bootcov and cph error
Hi all,
I am trying to get bootstrap resampled estimates of covariates in a Cox
model using cph (Design library).
Using the following I get the error:
> ddist2.abr <- datadist(data2.abr)
> options(datadist='ddist2.abr')
> cph1.abr <- cph(Surv(strt3.abr,loc3.abr)~cov.a.abr+cov.b.abr,
data=data2.abr, x=T, y=T)
> boot.cph1 <- bootcov(cph1.abr, B=100, coef.reps=TRUE,
2011 Apr 27
3
Kolmogorov-Smirnov test
Hi,
I have a problem with Kolmogorov-Smirnov test fit. I try fit distribution to
my data. Actualy I create two test:
- # First Kolmogorov-Smirnov Tests fit
- # Second Kolmogorov-Smirnov Tests fit
see below. This two test return difrent result and i don't know which is
properly. Which result is properly? The first test return lower D = 0.0234
and lower p-value = 0.00304. The lower 'D'
2007 Nov 29
1
Testing normality
Hi,
I'm doing kolmogorv-smirnov test but I don't know what conclusions to take, I want to know if my data has a normal distribution:
> ks.test(dados1,"pnorm")
One-sample Kolmogorov-Smirnov test
data: dados1
D = 0.972, p-value < 2.2e-16
alternative hypothesis: two-sided
Warning message:
cannot compute correct p-values with ties in: ks.test(dados1,
2006 Feb 03
2
Problems with ks.test
Hi everybody,
while performing ks.test for a standard exponential distribution on samples
of dimension 2500, generated everytime as new, i had this strange behaviour:
>data<-rexp(2500,0.4)
>ks.test(data,"pexp",0.4)
One-sample Kolmogorov-Smirnov test
data: data
D = 0.0147, p-value = 0.6549
alternative hypothesis: two.sided
>data<-rexp(2500,0.4)
2010 Nov 11
2
Kolmogorov Smirnov Test
I'm using ks.test (mydata, dnorm) on my data. I know some of my
different variable samples (mydata1, mydata2, etc) must be normally
distributed but the p value is always < 2.0^-16 (the 2.0 can change
but not the exponent).
I want to test mydata against a normal distribution. What could I be
doing wrong?
I tried instead using rnorm to create a normal distribution: y = rnorm
2011 Feb 19
3
Kolmogorov-smirnov test
Is the kolmogorov-smirnov test valid on both continuous and discrete data?
I don't think so, and the example below helped me understand why.
A suggestion on testing the discrete data would be appreciated.
Thanks,
a <- rnorm(1000, 10, 1);a # normal distribution a
b <- rnorm(1000, 12, 1.5);b # normal distribution b
c <- rnorm(1000, 8, 1);c # normal distribution c
d <- rnorm(1000,
2009 Apr 29
2
Kolmogorov-Smirnov test
I got a distribution function and a empirical distribution function. How do I
make to Kolmogorov-Smirnov test in R.
Lets call the empirical distribution function >Fn on [0,1]
and the distribution function >F on [0,1]
ks.test( )
thanks for the help
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2007 Nov 16
2
ks.test
Hello,
I want to do normality test on my data
I write this but I don't understand the display of the results
ks.test(data,"pnorm")
In fact I want to know if my data is a normal distribution. I have to check the p-value or D?
Thanks.
_____________________________________________________________________________
l
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2008 Jul 24
1
ggplot question
I am trying to do something simple with ggplot. I wish to draw a density
plot split by group, and fill each group with a different colour (and
each with an alpha =0.25). I have tried a number of variations of the
following, but cannot find a way to define the colour of the fill, its
transparency and the line around it individually - something in the
syntax continues to defy me.
2011 Jul 29
1
How to interpret Kolmogorov-Smirnov stats
Hi,
Interpretation problem ! so what i did is by using the:
>fit1 <- fitdist(vectNorm,"beta")
Warning messages:
1: In dbeta(x, shape1, shape2, log) : NaNs produced
2: In dbeta(x, shape1, shape2, log) : NaNs produced
3: In dbeta(x, shape1, shape2, log) : NaNs produced
4: In dbeta(x, shape1, shape2, log) : NaNs produced
5: In dbeta(x, shape1, shape2, log) : NaNs produced
6: In