Displaying 9 results from an estimated 9 matches for "gherardini".
2004 Oct 15
8
Testing for normality of residuals in a regression model
Hi all,
Is it possible to have a test value for assessing the normality of
residuals from a linear regression model, instead of simply relying on
qqplots?
I've tried to use fitdistr to try and fit the residuals with a normal
distribution, but fitdsitr only returns the parameters of the
distribution and the standard errors, not the p-value. Am I missing
something?
Cheers,
Federico
2005 Mar 01
2
Negative intercept in glm poisson model
Dear list,
I'm trying to fit a glm model using family=poisson(link = "identity"). The
problem is that the glm function fits a model with a negative intercept,
which sounds like a nonsense to me, being the response a Poisson variable.
>From a previous discussion on this list I've understood that the glm function
uses IRLS for the fitting without any constraint so it is
2004 Jul 28
3
Another big data size problem
Hi all,
I'm trying to read a 1220 * 20000 table in R but I'm having lot of problems. Basically what it happens is that R.bin starts eating all my memory until it gets about 90%. At that point it locks itself in a uninterruptible sleep status (at least that's what top says) where it just sits there barely using the cpu at all but keeping its tons of memory. I've tried with
2005 Jul 15
1
Padding in lattice plots
...ut I haven't been able to use them
properly. I've tried to input values between 0 and 1 as the padding value
(both left and right and top and bottom) but nothing changed. It seems I can
only increase the padding by using values > 1. Any ideas?
Thanks in advance for your help
Federico Gherardini
2004 Feb 23
1
Segmentation fault with fix() (PR#6605)
Full_Name: Federico Gherardini
Version: 1.8.1
OS: Gentoo linux
Submission from: (NULL) (81.208.36.89)
When I use fix() to edit a matrix R immediately quits with a segmentation fault
if I use the copy button in the graphical device window. Clicking on the name of
the variables completely messes up the screen too. In this case...
2004 Oct 26
3
Combining columns of different length
Hi,
you can use this simple function:
add.col<-function(df, new.col) {n.row<-dim(df)[1]
length(new.col)<-n.row
cbind(df, new.col)
}
see this example:
> x<-cbind(c(1,2,3),c(4,5,6))
> x
[,1] [,2]
[1,] 1 4
[2,] 2 5
[3,] 3 6
> y<-c(7,8)
> y
[1] 7 8
> add.col<-function(df, new.col)
2004 Oct 15
0
Re: Testing for normality of residuals in a regression model
Dear Federico,
see:
? shapiro.test(stats) Shapiro-Wilk Normality Test
and
? jarque.bera.test(tseries)
Jarque-Bera Test
They are the most common tests used for normality
testing.
Ciao
Vito
Federico Gherardini wrote on Fri Oct 15 14:44:18 CEST
2004:
Hi all,
Is it possible to have a test value for assessing the
normality of
residuals from a linear regression model, instead of
simply relying on
qqplots?
I've tried to use fitdistr to try and fit the
residuals with a normal
distribution, but fitdsit...
2004 Nov 25
1
Error using glm with poisson family and identity link
Hi all
I'm trying to use the function glm from the MASS package to do the
following fit.
fit <- glm(FP ~ rand, data = tab, family = poisson(link = "identity"),
subset = rand >= 1)
(FP is >= 0)
but I get the following error
Error: no valid set of coefficients has been found:please supply
starting values
In addition: Warning message:
NaNs produced in: log(x)
in contrast
2004 Jul 28
1
Fw: Another big data size problem
On Wed, 28 Jul 2004 09:53:08 +0200
Uwe Ligges <ligges at statistik.uni-dortmund.de> wrote:
>
> If your data is numeric, you will need roughly
>
> 1220 * 20000 * 8 / 1024 / 1024 ~~ 200 MB
>
> just to store one copy in memory. If you need more than two copies, your
> machine with its 512MB will start to use swap space .....
> Hence either use a machine with more