Displaying 7 results from an estimated 7 matches for "epsilon_i".
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2010 Feb 18
0
lme - incorporating measurement error with estimated V-C matrix
I have data (each Y_i is a vector) in the form of
Y_i = X_i \beta_i + Z_i b_i + epsilon_i
Were it not for the measurement error (the epsilon_i) it's a very
simple model --- nice and balanced, compound symmetry, and I'd just
use lme(y ~ x1 + x2, random=~1|subj, ...) but the measurement error is
throwing me off.
Because the Y_i are actually derived from other data, I am ab...
2010 Feb 01
2
numerical subscripts in a loop in a plot
...rying to create a graphic where I calculate the residual from a regression and want to mark each residual with its observation number. So something like
plot(0,0, type = "n", xlim = c(0,10))
for(i in 1:10){
text(i, 0, substitute(paste(epsilon[i])))
}
except that i end up pasting \epsilon_i 10 times and not \epsilon_1, ..., \epsilon_10. i'd be much obliged if anyone can put me out of my misery and let me know how i am goofing up.
many thanks
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2011 Aug 01
3
formula used by R to compute the t-values in a linear regression
...iable, t-value= b_k/sigma_k
With b_k is the coefficient for the k-th variable, and sigma_k =(t(x) x )^(-1) _kk is its standard deviation.
I find sigma_k = sigma * n/(n*Sum x_{k,i}^2 -(sum x_{k,i}^2))
With sigma: the estimated standard deviation of the residuals,
Sigma = sqrt(1/(N-K-1)*Sum epsilon_i^2)
With:
N: number of observations
K: number of variables
This formula comes from my old course of econometrics.
For some reason it doesn't match the t-value produced by R (I am off by about 1%). I can match the other results produced by R (coefficients of the regression, r squared, et...
2009 Oct 18
1
function to convert lm model to LaTeX equation
...*)", "", co), minlength=abbrev.length)
}
# Get and format DV
m.y <- strsplit((as.character(object$call[2])), " ~ ")[[1]][1]
# Write coefficent labels
b.x <- paste("\\beta_{", co.n ,"}", sep="")
# Write error term
e <- "\\epsilon_i"
# Format coefficint x variable terms
m.x <- sub("}Int","}", paste(b.x, co.n, " + ", sep="", collapse=""))
# If inline estimates convert coefficient labels to values
if(estimates == "inline") {
m.x <- sub("Int&quo...
2010 Apr 15
2
Regression w/ interactions
I have a project due in my Linear Regression class re: regression on a data
set & my professor gave us a hint that there were *exactly *2 sig
interactions. The data set is attached. We have to find which predictors are
significant, & which 2 interactions are sig. Also, I nedd some guidance for
this & selecting the best model. I tried the `full' model, that being:
2000 Aug 12
1
Nonlinear regression question
Dear R users
I recently migrated from Statistica/SigmaPlot (Windows) to R (Linux), so
please excuse if this may sound 'basic'.
When running a nonlinear regression (V = Vmax * conc / (Ks + conc), i.e.
Michaelis-Menten) on SigmaPlot, I get the output listed below:
>>>Begin SigmaPlot Output<<<
R = 0.94860969 Rsqr = 0.89986035 Adj Rsqr = 0.89458984
Standard Error of
2010 Apr 15
4
Does "sink" stand for anything?
Hello Everyone,
Learning about R and its wonderful array of functions. If it's not obvious, I usually try to find out what a function stands for. I think this helps me remember better.
One function that has me stumped is "sink." Can anyone tell me if this stands for something?
Thanks,
Paul
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