Displaying 20 results from an estimated 30000 matches similar to: "Normality test"
2008 Jul 24
4
Is there an equivalent * operator?
Hi all,
Is there an equivalent to the general * operator in R, where * can
represent any character?
I have a dataset, one column being date, date ranging between
April-September, 97-06. I would like to be able to acquire the data for
a specific month, say September, so that I can take average temperatures
for the month, etc. I thought I would be able to do something like
data.s1 <-
2008 Aug 21
4
Very confused with class
Hi all,
I am very confused with class.
I am looking at some weather data which I want to use as explanatory
variables in an lm. R has treated these variables as factors (i.e. with
different levels), whereas I want them treated as discretely measured
continuous variables. So I need to reassign the class of these
variables, right?
Indeed, doing
class(southwest$pressure)
(pressure being air
2008 Sep 08
3
Saving functions
Hi,
Appologies for the simple nature of this question, I am unable to find
the answer in manuals (EG and introduciton to R).
I have written a function in a text editor and saved it with an .R
extension. It is saved in my working directory. How can I run it, do I
need to use source? If so, how do I supply the arguments to the
function? Or does it need to be saved in a particular directory?
2008 Aug 18
2
Using lag
Dear all,
I am having difficulties using the seemingly-simple function lag.
I have a dataframe with several weather variables (maxitemp,
windspeed, rainfall etc), and the response variable (admissions). The
dataset is fairly large (1530 observations). I simply want to model the
response against a lag of a couple of the explanatory variables, say
maxitemp and rainfall. I would like to look at
2008 Jul 22
4
Opening files from R terminal - appologies
Dear all,
I appologise for cluttering up the list with such a basic question,
however I have been unable to find the answer I want (possibly through
my poor usage of the R help system).
As I am visually impaired and using assistive technology, I think I
would prefer to use R from the terminal mode, i.e. by running rterm.exe
found in the bin directory.
I have managed to set my working
2008 Jul 24
4
Just 2 more questions - for now!
Hi all,
Thanks for the help with my previous post.
I have just two more questions for the minute.
I think I said in a previous post that I like to use the terminal,
i.e. run rterm.exe. On exiting the terminal, I am asked if I want to
save the workspace. If I hit y (yes), the workspace is just saved as
.rdata in my working directory, does anyone know how I can name it
directly from the
2008 Sep 05
1
Orthogonalization algorithms
Hi,
I have eight vectors that I would like to orthogonalize preferably
using R. The vectors are of considerable length, however due to their
nature I know they satisfy the conditions needed to apply the
Gram-Schmidt algorithm. Before I embark on some R coding, I wanted to
check that there is no facility / function already around that computes
the orthogonalized set of vectors? I have performed
2008 Sep 04
2
Coefficient of skewness
Hi,
Is there a function in R to calculate the coefficient of skewness of
some data? I had expected there to be one, but can find no information
about it.
Thanks for any pointers.
Robin Williams
Met Office summer intern - Health Forecasting
robin.williams@metoffice.gov.uk
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2008 Aug 28
1
Renaming objects
Hi,
Is there any quick and easy way to rename a number of objects, without
having to rename each one individually and then remove the old one? And
if so, is there anything I can do to adjust the associated comments
accordingly?
Thanks for any help,
Robin Williams
Met Office summer intern - Health Forecasting
robin.williams@metoffice.gov.uk
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2008 Sep 09
2
How does predict.lm work?
Hi,
Please could someone explain how this element of predict.lm works?
From the help file
`
newdata
An optional data frame in which to look for variables with which to
predict. If omitted, the fitted values are used.
'
Does this dataframe (newdata) need to have the same variable names as
was used in the original data frame used to fit the model? Or will R
just look across consecutive
2008 Jul 21
1
Subsetting data by date
Hi all,
Firstly I appologise if this question has been answered previously,
however searching of the archives and the internet generally has not
yielded any results.
I am looking in to the effects of summer weather conditions
(temperature, humidity etc), on the incidences of a breathing disorder
brought on through smoking (COPD). I am fairly new to R and completely
new to the idea of
2009 Oct 22
1
Normality test
I am having a hard time interpreting the results of the 'shapiro.test' for normality. If I do ?shapiro.test I see two examples using rnorm and runif. When I run the test using rnorm I get a wide variation of results. Most of this may be from variability of rnorm, samll sample size (limited to 5000 for the test), etc but if I repeat the test multiple times I can get:
>
2008 Aug 28
1
Singularity?
Hi all,
When using lm to model a response with 8 explanatory variables, one of
the variables is not defined due to "singularities". I have checked the
csv file from which the data come, there are no na's in the dataset,
etc. What should I be looking for in this variable to correct the
problem?
Thanks for any help.
Robin Williams
Met Office summer intern - Health Forecasting
2009 May 04
2
normality test for large a large dataset ?
Hello,
Do you know a R implemented normality test like the shapiro test but more suitable for large data set ?
Thanks,
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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
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 :
>
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
2008 Sep 03
2
R update
Hi all,
please, someone can explain me how update my R version?
thank you!
giov
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2008 Sep 04
1
saving an object
Hi there,
I have a dataset stored in an object which has very huge volume of rows.I
want to reuse it for comparing with other datasets.I dont want it to reload
every time i run the script.Is there a way of saving a particular loaded
object in the workspace and reusing it.
Kindly help me.
Ramya Thulasingam
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2008 Sep 09
1
write dataframes
Hi,
After manipulate my data I have ended up with 5 different data frames
with different number of observations but the same
number of variables (columns)
An example, if I write str(object1), I see this,
data.frame': 47 obs. of 3 variables:
$ ORF : Factor w/ 245 levels "YAL038W","YAL054C",..: 10 19 38 39 44
45 50 51 59 60 ...
$ mRNA : num 0.891 1.148 1.202