Displaying 20 results from an estimated 40000 matches similar to: "image of expand.grid"
2001 Dec 18
4
chi-squared test
I don't quite understand the difference between the two methods for
performing a chi-squared test on contingency tables: summary(table())
and chisq.test()
They may different results. E.g.:
aa <- gl(2, 10)
bb <- as.factor(c(1,2,2,2,1,2,1,2,2,2,1,2,2,2,1,1,1,2,1,1))
aa <- c(aa, aa)
bb <- c(bb, bb)
table(aa, bb)
summary(table(aa, bb))
chisq.test(aa, bb)
Could somebody give me
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 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,
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
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$v[k]=m[i,j]
}
aa
}
Juli
2007 Feb 02
5
reading very large files
Hi all,
I have a large file (1.8 GB) with 900,000 lines that I would like to read.
Each line is a string characters. Specifically I would like to randomly
select 3000 lines. For smaller files, what I'm doing is:
trs <- scan("myfile", what= character(), sep = "\n")
trs<- trs[sample(length(trs), 3000)]
And this works OK; however my computer seems not able to handle
2008 Feb 10
2
reshape
Dear colleagues,
I'd like to reshape a datafame in a long format to a wide format, but
I do not quite get what I want. Here is an example of the data I've
have (dat):
sp <- c("a", "a", "a", "a", "b", "b", "b", "c", "d", "d", "d", "d")
tr <- c("A",
2003 May 01
4
var[i]
Dear all,
How could I use variables in a loop that their names are in a vector?
For example:
aaa <- 1:10
bbb <- aaa*2
ccc <- aaa+bbb
varn <- c("aaa", "bbb", "ccc")
m <- rep(NA, 3)
for (i in 1:length(varn)) m[i] <- mean(varn[i]) # wrong
thanks in advance
Juli
--
"Wars do not solve problems, wars generate even more problems"
2000 Mar 16
2
glm: offset in poisson
R-users,
Can an offset term be included in a Poisson model?
I get an error message when trying that:
>r3o <- glm(tax ~ areal + offset(o), family=poisson)
Error in (if (is.empty.model(mt)) glm.fit.null else glm.fit)(x = X, y = Y, :
inner loop 1; can't correct step size
In addition: Warning message:
Step size truncated due to divergence in: (if (is.empty.model(mt))
2008 Jun 26
1
write.table a df with specific column order
Hi
I'd like to write.table a dataframe, but with an specific order of
columns. Is there a direct way to do it? or I have to generate a new
dataframe as follows:
t <- data.frame(c=1:10, b=11:20, a=letters[1:10])
t2 <- data.frame(a=t$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
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,
2003 May 08
2
Expanding upon expand.grid()
Hello All:
The function expand.grid() does nearly exactly what I want for
permutation tests I wish to carry out, and it does so quickly when the
number is kept small as in the example below:
expand.grid(rep(list(c(-1, 1)), 3))
Var1 Var2 Var3
1 -1 -1 -1
2 1 -1 -1
3 -1 1 -1
4 1 1 -1
5 -1 -1 1
6 1 -1 1
7 -1 1 1
8 1 1 1
Understandably,
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 <-
2002 Sep 05
4
line thickness in plots
Hi all,,
Is it possible to set a thicker line for the box around the plots? (i.e.
for the four axes)
Something like lwd (lines) but for the box.
Thanks
juli
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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()
2012 Mar 15
1
expand.grid using a matrix and a vector as input
Hello R-users,
I have the following question, for which my search did not really return any usable result.
If I have a matrix a1, and a vector a2 like below
a1<-matrix(c(1:4),2,2)
a2<-c(8,9)
is there any function like the expand.grid (or some clever calling of the function) such that it outputs a matrix or dataframe where the entire a1 matrix is repeated for each value of a2 (the
2004 Jan 21
2
subset select within a function
Dear all,
I'd like to subset a df within a function, and use select for choosing
the variable. Something like (simplified example):
mydf <- data.frame(a= 0:9, b= 10:19)
ttt <- function(vv) {
tmpdf <- subset(mydf, select= vv)
mean(tmpdf$vv)
}
ttt(mydf$b)
But this is not the correct way. Any help?
Thanks in advance
Juli
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