Displaying 20 results from an estimated 800 matches similar to: "t-test with autocorrelation correction"
2007 Jun 19
2
Preconditions for a variance analysis
Hello everbody,
i'm currently using the anova()-test for a small data.frame of 40 
rows and 2 columns. It works well, but is there any preconditions for 
a valid variance analysis, that i should consider?
Thank you for your answer,
Daniel
2006 Nov 15
1
how to compute p-value?
Hi all,
I just want to understand how R computes p-value in a simple linear
regression model? The reason is that in Matlab in the
function which "evaluate standard errors for multivariate normal
regression", it just provide estimates and standard errors, without giving
out p-value,
It computes t-statistics as follows:
abs(beta_hat/std_beta_hat)
how to go further to get p-value?
2006 Nov 06
2
comparing 2 dataframes
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2007 Jan 03
1
mathematical symbols in plots
Hello everyone!
I'm trying to plot some mathematical expression along my axis, but
demo(plotmath) did not have the symbol I was looking for. In particular,
I would like to denote the mean of an observable by writing
<k>
which I tried to enter with
expression(group("<", k, ">"))
However, my naive try doesn't work and the help doesn't want to tell me,
2007 Feb 27
1
prop.test or chisq.test ..?
Hi everyone,
Suppose I have a count the occurrences of positive results, and the total 
number of occurrences:
pos <- 14
total <- 15
testing that the proportion of positive occurrences is greater than 0.5 gives 
a p-value and confidence interval:
prop.test( pos, total, p=0.5, alternative='greater')
        1-sample proportions test with continuity correction
data:  14 out of
2007 Jun 16
1
Lines connecting the boxes in a boxplot
Hello,
I'm currently using a boxplot to visualize data for three different
models. As I have three models, I'm plotting three parallel boxplots
for each factor.
This works fine - what I need now is a line connecting the medians of
each boxplot of each model. I want to do this in order to visualize
the trend that one of the models exhibit. Basically, I want to plot a
curve for each model
2007 Jan 20
1
aov y lme
Dear R user,
I am trying to reproduce the results in Montgomery D.C (2001, chap 13, 
example 13-1).
Briefly, there are three suppliers, four batches nested within suppliers 
and three determinations of purity (response variable) on each batch. It is 
a two stage nested design, where suppliers are fixed and batches are random.
y_ijk=mu+tau_i+beta_j(nested in tau_i)+epsilon_ijk
Here are the
2006 Sep 22
2
Merge problem
Hello all,
I have read as many merge issues as I possibly could tonight and  
although I presume this is a small error, I have not found the  
solution to my problem.
I'm trying to merge two data sets: dat0 and TransTable.  As you can  
see below, dat0 has 8000 rows, whereas TransTable has 47296 rows.  I  
would expect when I merge the two data sets, with all.x=F, and  
all.y=F, that the
2007 Jan 23
3
the value of Delta
Dear all,
I am running R 2.4.1.
> library(siggenes);
> library(multtest);
> cl<-rep(c(0,1),c(3,3));
> sub<-exprs(AffyExpData[,c(1:3,7:9)]);
> gn<-geneNames(AffyRAwData);
> sam.out<-sam(sub,cl,rand=123,gene.names=gn);
We're doing 20 complete permutations
> sam.out
SAM Analysis for the Two-Class Unpaired Case Assuming Unequal Variances 
 
   Delta    p0 
2007 Jun 12
2
Data transformation for chi-square test.
Dear all R users
:
I am a IT student with few statistical background and new R user for only 
have  two month exprience. I have a data named medcost, import by 
read.table() as follow for example (real dataset has 500 cases), the 
heander id means case id, member means members in a family and cost is the 
family pay for medical cost every 6 months.
id        member               cost
1         4 
2006 Nov 07
3
question on multilevel modeling
Hi,
 
I am trying to run a multilevel model with time nested in people and
people nested in dyads (3 levels of nesting) by initially running a
series of models to test whether the slope/intercept should be fixed or
random.  The problem that I am experiencing appears to arise between the
random intercept, fixed slope equation AND.
 
(syntax:
rint<-lme(BDIAFTER~BDI+WEEK+CORUMTO,
2011 Apr 12
1
How to set the dimension of a matrix correctly?
Hi all,
I use kriging to interpolate the precipitation from stations,  but the map of this results show lots of stripes. (please see the attachment)I think there's something wrong with the setting of the dimension of this matrix, however, I have no idea how to know or test to see if this setting is correct or not.I've tried to switch the latitude and longitude, but still got the same
2005 Dec 21
0
Help with Krige.conv using linear models
A majority of my data makes a kriged map perfectly using an exponential 
model for the semivariogram to fit my data and then going through the 
commands variofit() to define the model and then krige.conv() to use the 
model to predict values in a grid.  But?one set of my data appears to be 
linearly correlated for the first 5000 meters and not correlated beyond 
that. I have been having problems
2006 Mar 15
2
difftime arguments
Hi
    I just started using RGui.exe under widnows.
  I have a text file containing date arranged in columns and rows, each column has the same format, each row with different formats. 3 of the columns are something like this 1/12/2006 3:59:45 PM
  I need to calculate the different in seconds between 2 selected periods using their row’s index
   
  My solution:
  Read the file in a data frame and
2006 Oct 23
1
Worm distribution :-)
You are talking about random point patterns, since the glow-worms
appear as ``stars'' (= points).   See the package ``spatial'' (which
comes with R) and try simulating a pattern using Strauss().
Or install the package ``spatstat'' from CRAN --- in this package
there is a variety of ways to simulate ``regular'' random point
patterns --- rMaternI, rMaternII, rSSI,
2005 Jan 17
1
merge data frames taking mean/mode of multiple macthes
Hello :)
I have two data frames, one has properties taken on a
piece by piece basis and the other has performance on
a lot by lot basis. I wish to combine these two data
frames but the problem is that each lot has multiple
pieces and hence i need to take a mean of the
properties of multiple pieces and match it to the row
having data about the lot.
I was wondering if there is a simple commmand,
2006 Sep 25
1
apply: new behaviour for factors in R-2.4.0
Dear R-core
There is a different output for the apply function due to the
change of unlist as mentioned in the R news.
Newly, applying as.factor() (or factor()) in
str(dat <- data.frame(x = 1:10, f1 = gl(2,5,labels = c("A", "B"))))
(d1 <- apply(dat,2,as.factor))
newly returns a character matrix while in R-2.3.1 the same
command resulted in an integer matrix that was
2006 Apr 25
1
summary.lme: argument "adjustSigma"
Dear R-list
I have a question concerning the argument "adjustSigma" in the
function "lme" of the package "nlme". 
The help page says:
"the residual standard error is multiplied by sqrt(nobs/(nobs - 
npar)), converting it to a REML-like estimate."
Having a look into the code I found:
stdFixed <- sqrt(diag(as.matrix(object$varFix)))
if (object$method
2005 May 15
3
adjusted p-values with TukeyHSD?
hi list,
i have to ask you again, having tried and searched for several days...
i want to do a TukeyHSD after an Anova, and want to get the adjusted  
p-values after the Tukey Correction.
i found the p.adjust function, but it can only correct for "holm",  
"hochberg", bonferroni", but not "Tukey".
Is it not possbile to get adjusted p-values after
2006 Jan 18
3
linear contrasts with anova
I have some doubts about the validity of my procedure to estimeate linear contrasts ina a factorial design.
For sake of semplicity, let's imagine a one way ANOVA with three levels. I am interested to test the significance of the difference between the first and third level (called here contrast C1) and between the first and the seconda level (called here contrast C2). I used the following