Displaying 20 results from an estimated 3000 matches similar to: "R: to the power"
2005 Oct 05
1
(no subject)
hi all
why does the following not work???
this was someone elses code and i couldnt explain why it doesn't work.
m=matrix(c(0,0),2,1)
v=matrix(c(1,0,0,1),2,2)
Y=function(X1,X2,mu=m,V=v)
{
X=matrix(c(X1,X2),2,1)
a=(1/((2*pi)*sqrt(det(V))))*exp((-0.5)*(t(X-mu)%*%solve(V)%*%(X-mu)))
a[1]
}
x1=seq(-1,1)
x2=x1
Z=outer(x1,x2,FUN="Y",mu=m,V=v)
persp(x1,x2,Z)
my code:
2004 Feb 10
6
R: lags
hi all
how does one simulate a random walk process?
i.e
y(0)=0
y(t)=y(t-1)+ e(t)
where e(t) is normal(0,1) say.
Regards
allan
2005 Jul 29
5
R: graphics devices
a simple question
how does one produce plots on two different graphics devices?
/
allan
2004 Jan 05
4
r: lm question
Hi all
this is a silly question since i should know the answer.
lm(y~x) perfroms linear regression with the intercept included.
How do i estimate the equation without the intercept?
cheers
2005 Mar 04
11
R: simulation
hi all
a simple question
i want to run simulations in r. i however want the experiments to be
repeated at a later time with exactly the same numbers by other users.
can i set the random number seed for rnorm in some way?
e.g. is there some arguement that goes with rnorm?
please supply an example
regards
Allan
2004 Feb 03
4
R: lags and plots
Hi all
I want to calculate certain lags of a time series and plot them
simultaneously on a graph. can anyone help?
2010 Feb 11
1
Fwd: Recall function: "evaluation nested too deeply: infinite recursion / options(expressions=)?"
hello all
i searched the archives and couldn't get a solution to the following question.
i have the following function:
F=function(z,v)
{
if (v==-.5) return(1) else return(2*v/z + 1/Recall(z,v-1))
}
and while testing whether it works (ie F(z,v) is approx = besselK(z,1+v)/besselK(z,V). the recursion formula allows one to calculate besselK(z,1+v)/besselK(z,V) for large values of z )
2005 Aug 11
3
sub set selection
hi all
is there a package that undertakes subset selection but BASED ON AIC or
any other information criteria.
i've seen the "subselect" and the "leaps" package but i have not played
around with them yet.
thanx
2008 Jan 22
1
R: determinants and inverses
hello all
sorry for the following "none" R related question.
does anyone know of a reference to calculate the following identity:
|I + ABC|
where I is an identity matrix and A, B,C may not have to be square matrices?
you help will be greatly appreciated.
H. V. Henderson; S. R. Searle
SIAM Review, Vol. 23, No. 1. (Jan., 1981), pp. 53-60.
provides a result to
2005 Sep 15
2
R: deleting rows
hi all
hopefully some one can help.
assume that i imported the following data into R (say the data frame is
called a)
x1 x2 x3
1 NA 3
1 2 NA
1 2 3
3 NA 6
4 5 9
7 5 6
7 8 9
NA 7 9
How can i construct a new data frame that only contains those rows that
does not contain the NA's? is these a quick way?
ie
x1 x2 x3
1 2 3
4 5 9
7 5 6
7 8 9
in this example we can simple use
2004 Sep 29
3
R: string connections
hi all
i have a simple question:
lets assume that i can enter a variable (a) equal to some value, say
100. obviously a could be any value. i would like to create a plot with
a main heading as
hi all
"some writing" + a
how would own create a string by combining a string with a numeric
variable?
hope the question is not too confusing.
e.g. say a=5 then i want something like
2004 Feb 24
5
r: plots
hi all
i have another probably simple question.
I have three variables say x, y and z. x and y are quite large and z is
relative small.
how can one plot the three variables on the same graph with two separate
axis?
(one for x and y and the other for z)
e.g.
x<-c(101,110,150,167,120)
y<-c(120,135,175,95,200)
z<-c(0.001, 0.15, 0.6, 0.8, 1)
regards
Allan
2004 Feb 03
3
R: plotting multiple functions
Hi all
Another simple question.
I would like to plot three graphs one the same plot with different
colours. Say red, blue and black. Here are the functions.
r1<-1+5*cos(2*pi*seq(1:100)/20)+rnorm(100)
r2<-1+7*sin(2*pi*seq(1:100)/20)+rnorm(100)
r3<-1+7*sin(2*pi*seq(1:100)/20)+5*cos(2*pi*seq(1:100)/20)+rnorm(100)
Regards
Allan
2005 Sep 05
3
numerical intergation
how does one numerically intergate the following:
A=function(x,y)
{
xy
}
over the range: 2<x<0 4<y<10
say.
ie how would one set up the integrate function?
i forgot!
2005 Jul 29
1
R: non parametric regression/kernels
hi all
i have a another stats question.
i would like to solve the following question:
y(i)=a+b*x(i)+e(i)
i.e. estimate a and b (they should be fixed) but i dont want to specify
the standard density to the straight line.
this can be done using kernel regression. the fitted line is however
fitted locally. does anyone have a reference that will help me with my
problem.
i am still new to
2005 Apr 11
4
R: function code
HI
sorry to be a nuisance to all!!!
how can i see the code of a particular function?
e.g. nnet just as an example
2004 May 13
1
factor analysis
hi all
this is a stats question.
when undertaking factor analysis should the variables included always be
continiuos random variables? could one include categorical data? e.g
some survey type data
my gut feeling is that one should not include categorical type data
since factor analysis is based on the eigenanalysis of the correlation
matrix of a group of variables. The introduction of
2005 Dec 31
1
r: RODBC QUESTION
hello all
i have a quick question. i have been using the RODBC library (trying to
read Excel data
into R but i am doing this by using Rexcel. this is probably not the
correct forum -
sorry for this).
my code is shown below:
Sub A()
'start the connection to R
Call RInterface.StartRServer
RInterface.RRun "library(RODBC)"
RInterface.RRun "A =
2009 Feb 23
1
r: intergrate behaviour
hello R users
strange behavior of the integrate function!
i assume this occurs because of the way in which the quadriture is set up! (any comments.)
f=function(x){exp(-exp(-x)-5*x)/gamma(5)}
xx=seq(from=-20, to=20, length.out=1000)
plot(xx,f(xx),type="l")
integrate(f, lower=-Inf, upper= 1)
integrate(f, lower=-Inf, upper= 10)
integrate(f, lower=-10, upper= 11)
integrate(f,
2006 Oct 09
1
winbugs - R question
hi all
i would like to use r and winbugs in order to undertake seemingly unrelated regression. i am using the R2WINBUGS library. i just simulated a simple example (sample size is 25) in order to get the correct code.
i suspect that the problem is in my definition of the prior. it wants a multivariate node.
the example could be extended by including more than 1 X variable in the system of