Displaying 20 results from an estimated 5000 matches similar to: "three short questions"
2003 Oct 27
3
expanding factor with NA
I have a factor (with "n" observations and "k" levels), with only
"nobs" < n of the observations not missing. I would like to produce a
(n x k) model matrix with treatment contrasts for this factor, with
rows of NAs placeholding the missing observations. If I use
model.matrix() I get back a (nobs x k) matrix. Is there an easy way
to get the (n x k) without
2002 Aug 29
8
lme() with known level-one variances
Greetings,
I have a meta-analysis problem in which I have fixed effects
regression coefficients (and estimated standard errors) from identical
models fit to different data sets. I would like to use these results
to create pooled estimated regression coefficients and estimated
standard errors for these pooled coefficients. In particular, I would
like to estimate the model
\beta_{i} = \mu +
2003 Jun 19
2
Fitting particular repeated measures model with lme()
Hello,
I have a simulated data structure in which students are nested within
teachers, and with each student are associated two test scores. There
are 20 classrooms and 25 students per classroom, for a total of 500
students and two scores per student. Here are the first 10 lines of
my dataframe "d":
studid tchid Y time
1 1 1 -1.0833222 0
2 1 1
2004 Jan 30
1
Measures of central tendency - mode
Greetings,
This seems too rudimentary to ask but for the life of me I cannot locate a readily easy method to compute the univariate mode. I know "mode" is not correct and "table" provides a reasonable count but I figured there would be an easy way to extract the value from the table after I do something like:
max(table(mydadat$myvar))
unfortunately it only returns the max
2003 Jan 02
3
random number generation
Can a single random number be generated in R? I have an exercise that wants
to simulate coin tosses, and I cannot seem to find a good example of the use
of random number generation in R. Any help?
Joshua Gramlich
Chicago, IL
2003 Jan 23
1
subset dataframe based on rows
I want to subset the dataframe based on certain values in a row.
for each row in my dataframe
if ANY one value of a particular set of columns satisfies cond
append a logical value true at the end of the row
else
append a false at the end of the row
in the end I want to be able to subset the whole data based on the
appended true or false value.
I could literally code like this, but I think
2003 May 30
2
Extracting Vectors from Lists of Lists Produced by Functions
If you found my subject heading to be confusing then I'm sure you'll enjoy
the example I've included below. I find the apply type functions to be
wonderful for avoiding loops but when I use them with existing functions, I
end up using loops anyway to extract the vectors I want. I would appreciate
it if someone could show me how to avoid these loops. Thanks.
EXAMPLE:
2003 Mar 05
8
how to find the location of the first TRUE of a logical vector
without having to check the vector element by element? Thanks a lot!
Jason
=====
Jason G. Liao, Ph.D.
Division of Biometrics
University of Medicine and Dentistry of New Jersey
335 George Street, Suite 2200
New Brunswick, NJ 08903-2688
phone (732) 235-8611, fax (732) 235-9777
http://www.geocities.com/jg_liao
2002 Jul 02
3
mean and array
In general this is what "apply" does. In your example you could use
rowMeans(ar) as well, I think.
Reid Huntsinger
-----Original Message-----
From: Olivier Martin [mailto:olivier.martin at inrialpes.fr]
Sent: Tuesday, July 02, 2002 10:55 AM
To: r-help
Subject: [R] mean and array
Hi all,
I have an array, one say ar, with 3 dimensions.
dim(ar)
>200 3 4
I would like to
2003 Jul 22
1
Making a group membership matrix
Hi Helpers:
I have a factor object that has 314k entries of 39 land cover types.
(This object can be coerced to characters neatly should that be easier
to work with.)
> length(foo)
[1] 314482
> foo[1:10]
[1] Montane Chaparral Barren Red Fir Red Fir
[5] Red Fir Red Fir Red Fir Red Fir
[9] Red Fir Red Fir
39 Levels:
2002 Mar 05
3
newbie: remove column with low mean from a matrix
Dear all,
Sorry to bother you with one more newbie question.
I have a dataobject with several hundreds of columns. I want to remove
columns with a mean of the column values below a certain value:
> a<- c(1,2,3,4,5,6)
> b<-c(2,4,6,8,10,12)
> c<- c(3,6,9,12,15,18)
> test<- as.matrix(cbind(a, b, c))
> mean(a)
[1] 3.5
> mean(b)
[1] 7
> mean(c)
[1] 10.5
Say the
2002 Oct 13
3
R process size growing in time...
Dear all,
I observed that the R process is growing in time (I was working with
the same session for two days, and the size reached 300 Mb). Explicit
calls to 'gc()' did show a trigger around 90 Mb but did not change
the RSS (while I remembered that my linux was nicely behaving before
and the process size was shrinking when R was freeing memory...). I
ended up saving the session, ending it
2003 Jun 25
2
within group variance of the coeficients in LME
Dear listers,
I can't find the variance or se of the coefficients in a multilevel model
using lme.
I want to calculate a Chi square test statistics for the variability of the
coefficients across levels. I have a simple 2-level problem, where I want to
check weather a certain covariate varies across level 2 units. Pinheiro
Bates suggest just looking at the intervals or doing a rather
2002 Jun 18
5
insert number in vector
Hello R-users,
I need to create a vector inserting an 1 after each value of another vector.
For example:
vec1<-c(2,3,4)
I need to create a vector with the values 2,1,3,1,4
Does anyone know how create this vector without loops (vec1 could have 1000
elements)
Thank you,
Juan
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r-help mailing list -- Read
2002 Feb 28
3
R-plots with 'complex' axis-labelling
Hi there,
I want to create plots with some kind of 'complex' axis labelling of the form
$\dot{V}$ and integrate those plots into a LaTeX document. What is the best
way to go?
I've figured out, that the 'plotmath' commands are somewhat limited (at least
I wasn't able to get the $\dot{V}$ generated) and that plots with
'plotmath'-axes wouldn't export
2005 May 27
4
plotting box plots on same x
I am trying to construct a graph of 6 box plots of blood pressures. I
want them to be on a single set of axis and I want the SBP to be ontop
of the DBP. I have an array bp with the data in it and I tried
a[1,]<-c(145,60,147,62,140,57)
a[2,]<-c(160,75,160,74,160,70)
a[3,]<-c(140,55,140,65,142,55)
boxplot(data.frame(a), main = "Blood Pressures", at=c(1,1,2,2,3,3),
2002 Sep 09
1
getting variable names into formulas
Hello,
I have a dataframe with several hundred variables. I would like to
explore updates of some baseline lme fit by including each of some
subset of these variables, one at a time. For various reasons it is
inconvenient to rely on the positions of the numbered columns in the
dataframe. Here is what I want to do:
mod.baseline<-lme(fixed=foo,data=dat,random=bar)
for(thisvar in vars){
2004 Oct 06
1
odd behavior of summary()$r.squared
I may be missing something obvious here, but consider the following simple
dataset simulating repeated measures on 5 individuals with pretty strong
between-individual variance.
set.seed(1003)
n<-5
v<-rep(1:n,each=2)
d<-data.frame(factor(v),v+rnorm(2*n))
names(d)<-c("id","y")
Now consider the following two linear models that provide identical fitted
values,
2009 Apr 23
2
Plots - several pages per pdf - quality/size issue
Dear R-experts,
I hope that question will not be too redundant (sorry if it is) but i don't seem able to find the answer i need in the archives...
I try to create a file which would have 1.several pages and 2.several plots by page. I know how to make a pdf file this way, but my problem is that the pdf size gets way too big and cannot be open.
So my question is:
- is there a way to diminish
2009 May 03
2
clear screen?
I?ve been using this routine for several years. I?m sorry, I don?t remember
where I got it. It works as it should, viz. it blanks the R console. But
it requires package rcom and now that requires rscproxy.
cls <-
function ()
{
require(rcom)
wsh <- comCreateObject("Wscript.Shell")
comInvoke(wsh, "SendKeys", "\f")
invisible(wsh)
}
> cls()