Displaying 20 results from an estimated 5000 matches similar to: "chi-squared test"
2001 Sep 25
2
glm.nb, anova.negbin
Dear R-collegues,
I'm getting an error message (Error in round) when summarising a glm.nb
model, and when using anova.negbin (in R 1.3.1 for windows):
> m.nb <- glm.nb(tax ~ areal)
> m.bn
Call: glm.nb(formula = tax ~ areal, init.theta = 5.08829537115498,
link = log)
Coefficients:
(Intercept) areal
3.03146 0.03182
Degrees of Freedom: 283 Total (i.e. Null); 282
2003 Apr 24
1
matrix to coordinates
Dear R-users,
I'm sure it must be a specific function or a better way to convert
matrix to x,y,z coordinates (and viceversa), than my function below (it
works). Any help?
m2coord <- function(m)
{
k <- nrow(m)*ncol(m)
aa <- data.frame(r=1:k, c=1:k, v=1:k)
k <- 0
for (i in 1:nrow(m))
for (j in 1:ncol(m))
{
k <- k+1
aa$f[k]=i; aa$c[k]=j; aa$v[k]=m[i,j]
}
aa
}
Juli
2002 May 11
2
RODBC sqlFetch
Hi,
Thanks for showing me how to use RODBC and odbcConnect.
Now works nicely. The question I've got now is:
noms <- list.files(pattern=".DBF")
# removing extension names:
noms <- sapply(noms, function(x) as.character(strsplit(x,".DBF")) ,
USE.NAMES=F)
for (i in 1:length(noms)) {
s <- sqlFetch(bdades, noms[i])
# etc.
}
But it seems that sqlFetch()
2003 Dec 18
2
barplot & plot together
Dear colleges,
I'm trying to combine a barplot and a plot in a single figure as follows:
data <- 1:6
t <- barplot(data, axes=F)
par(new= T)
plot(t, data, type="b")
However, as you can see in the example, the dots of the second plot do
not fall in the midpoint of the bars in the first. Any trick for setting
the 2 plots at the same scale?
I have unsuccessfully tried:
plot(t,
2001 Sep 11
2
AIC
Dear R collegues,
I'm trying to understand what's AIC in R (ver. 1.3.1), and I'm getting a
different answer if I look at the AIC(of the fitted model) or the aic in
the summary( of the fitted model). Is this correct? Can somebody explain
me the difference between the two values? or Is the AIC criterion not
appropiated for Poisson models?
R session:
> t1 <- glm(tax ~ areal,
2001 Sep 11
2
AIC
Dear R collegues,
I'm trying to understand what's AIC in R (ver. 1.3.1), and I'm getting a
different answer if I look at the AIC(of the fitted model) or the aic in
the summary( of the fitted model). Is this correct? Can somebody explain
me the difference between the two values? or Is the AIC criterion not
appropiated for Poisson models?
R session:
> t1 <- glm(tax ~ areal,
2000 Mar 16
2
glm: offset in poisson
R-users,
Can an offset term be included in a Poisson model?
I get an error message when trying that:
>r3o <- glm(tax ~ areal + offset(o), family=poisson)
Error in (if (is.empty.model(mt)) glm.fit.null else glm.fit)(x = X, y = Y, :
inner loop 1; can't correct step size
In addition: Warning message:
Step size truncated due to divergence in: (if (is.empty.model(mt))
2002 Jan 08
6
Subsets without NA
Is there a way of removing all rows with missing values from a data frame?
I usually use
subset(x, var1!="NA")
and repeat for each variable. It would be nice to be able to do it in one
fell swoop. Also, surprisingly, it doesn't always work. Sometimes I'm left
with an empty set even though not all rows have missing values for the
variable.
Cheers,
mikkel
Mikkel Grum,
2002 Jul 30
4
chisq.test, basic question
The cells are interpreted as counts, so by scaling you're analyzing a
different experiment (one with fewer observations). So the chi-squared value
will change (the terms (O-E)^2/E in the statistic scale linearly ignoring
rounding and "Yates' continuity correction").
The chisq.test on the original data is a test of association. Conventionally
you decide ahead of time on a
2008 Feb 27
1
glm binomial with no successes
Dear all,
I have a question on glm, family binomial. I do not see significant
differences between the levels of a factor (treatment) if all data for
a level is 0; and replacing a 0 for a 1 (in fact reducing the
difference), then I detect the significant difference that I expected.
Is there a way to overcome this problem? or this is an expected
behaviour ? Here is an example:
s <-
2005 Oct 04
1
repeated measures with random effects
Dear all,
I'm interested in analysing a reapeated measure desing where plant
height (H) was measured 3 times (Time). The experimental design
include 2 fixed factor (say A and B) in which A is nested in B, and a
random factor (C, the plot), using the aov().
So my first idea would be something like:
aov(H ~ B * A %in% B * Time + Error(id) )
where id is the factor coded for the repeated
2011 Jun 03
1
R and DBSCAN
Hello everyone,
When looking for information about clustering of spatial data in R I was
directed towards DBSCAN. I've read some docs about it and theb new
questions have arisen.
DBSCAN requires some parameters, one of them is "distance". As my data
are three dimensional, longitude, latitude and temperature, which
"distance" should I use? which dimension is related to
2007 Feb 02
5
reading very large files
Hi all,
I have a large file (1.8 GB) with 900,000 lines that I would like to read.
Each line is a string characters. Specifically I would like to randomly
select 3000 lines. For smaller files, what I'm doing is:
trs <- scan("myfile", what= character(), sep = "\n")
trs<- trs[sample(length(trs), 3000)]
And this works OK; however my computer seems not able to handle
2008 Feb 10
2
reshape
Dear colleagues,
I'd like to reshape a datafame in a long format to a wide format, but
I do not quite get what I want. Here is an example of the data I've
have (dat):
sp <- c("a", "a", "a", "a", "b", "b", "b", "c", "d", "d", "d", "d")
tr <- c("A",
2011 Jul 13
7
Extraer datos mensuales de una serie temporal
Hola a todos
Estoy intentando extraer un subconjunto de datos de una serie temporal,
concretamente quiero extraer los meses de verano de varios años pero no
encuentro la manera. Los datos tienen este formato:
FECHA;H_SOLAR;DIR_M;DIR_S;VEL_M;VEL_S;VEL_X;U;V;TEMP_M;HR;BAT;PRECIP;RAD;UVA;UVB;FOG;GRID;
2008 Jun 26
1
write.table a df with specific column order
Hi
I'd like to write.table a dataframe, but with an specific order of
columns. Is there a direct way to do it? or I have to generate a new
dataframe as follows:
t <- data.frame(c=1:10, b=11:20, a=letters[1:10])
t2 <- data.frame(a=t$a, b=t$b, c=t$c)
write.table(t2, row.names=F)
Thanks for any comment
Juli
--
http://www.ceam.es/pausas
2008 Jun 27
1
removing blanks from a string
Hi
Is there a way to remove blank characters from the end of strings in a
vector? Something like the =TRIM functions of the OpenOffice
spreadsheet. E.g.,
a <- c("hola ", "Yes ", "hello ") # I'd like to get:
c("hola", "Yes", "hello")
Thanks
Juli
--
http://www.ceam.es/pausas
2007 Apr 25
1
Help with saptial analysis (cluster)
Hi R-users
I'm a beginner with R and statistics, so I need some help to start my data
analysis. I've been reading some docs and tutorials on R and cluster analysis.
I've got a large dataset (102000 points) with values of longitude, latitude and
temperature and want to see if I can find groups (clusters).
Following some tutorials I can look for principal components but get an error
2011 Mar 04
3
Análisis de una serie temporal diaria
Hola a todos
Estoy tratando de analizaruna serie temporal con datos diarios de
temperaturas (40 años). He creado un objeto zoo (con ayuda de la lista,
gracias) sobre el que encuentro la regresión lineal. He probado también
a crear un objeto ts a partir del zoo. El problema que encuentro es que
nose puede aplicar la función stl para hallar la componente estacional y
la tendencia. Rdice que la
2010 Jun 14
1
Install Rmpi
Hi everyone
As I couldn't succeed with manual installation of Rmpi I decided to
start again from the beginning. I removed R and MPICH in my Ubuntu Hardy
installation. Then, to avoid any dependencies problems I have installed
MPICH and R from synaptic, not from sources. But now I can't install Rmpi.
An error message appears when trying to install Rmpi, you can find in