Displaying 20 results from an estimated 1000 matches similar to: "System of related regression equations"
2011 Apr 12
2
Testing equality of coefficients in coxph model
Dear all,
I'm running a coxph model of the form:
coxph(Surv(Start, End, Death.ID) ~ x1 + x2 + a1 + a2 + a3)
Within this model, I would like to compare the influence of x1 and x2 on the
hazard rate.
Specifically I am interested in testing whether the estimated coefficient
for x1 is equal (or not) to the estimated coefficient for x2.
I was thinking of using a Chow-test for this but the Chow
2010 Nov 11
2
predict.coxph and predict.survreg
Dear all,
I'm struggling with predicting "expected time until death" for a coxph and
survreg model.
I have two datasets. Dataset 1 includes a certain number of people for which
I know a vector of covariates (age, gender, etc.) and their event times
(i.e., I know whether they have died and when if death occurred prior to the
end of the observation period). Dataset 2 includes another
2011 Mar 26
1
Effect size in multiple regression
Dear all,
is there a convenient way to determine the effect size for a regression
coefficient in a multiple regression model?
I have a model of the form lm(y ~ A*B*C*D) and would like to determine
Cohen's f2 (http://en.wikipedia.org/wiki/Effect_size) for each predictor
without having to do it manually.
Thanks,
Michael
Michael Haenlein
Associate Professor of Marketing
ESCP Europe
Paris,
2016 Apr 16
1
Social Network Simulation
Dear all,
I am trying to simulate a series of networks that have characteristics
similar to real life social networks. Specifically I am interested in
networks that have (a) a reasonable degree of clustering (as measured by
the transitivity function in igraph) and (b) a reasonable degree of degree
polarization (as measured by the average degree of the top 10% nodes with
highest degree divided by
2011 May 13
6
Powerful PC to run R
Dear all,
I'm currently running R on my laptop -- a Lenovo Thinkpad X201 (Intel Core
i7 CPU, M620, 2.67 Ghz, 8 GB RAM). The problem is that some of my
calculations run for several days sometimes even weeks (mainly simulations
over a large parameter space). Depending on the external conditions, my
laptop sometimes shuts down due to overheating.
I'm now thinking about buying a more
2013 Jan 22
2
Approximating discrete distribution by continuous distribution
Dear all,
I have a discrete distribution showing how age is distributed across a
population using a certain set of bands:
Age <- matrix(c(74045062, 71978405, 122718362, 40489415), ncol=1,
dimnames=list(c("<18", "18-34", "35-64", "65+"),c()))
Age_dist <- Age/sum(Age)
For example I know that 23.94% of all people are between 0-18 years, 23.28%
2009 Mar 16
2
FW: Select a random subset of rows out of matrix
Dear all,
I have a large dataset (N=100,000 with 89 variables per subject). This dataset is stored in a 100.000 x 89 matrix where each row describes one individual and each column one variable.
What is the easiest way of selecting a subset of let's say 1.000 individuals out of that whole matrix?
Thanks,
Michael
Michael Haenlein
Associate Professor of Marketing
ESCP-EAP European School of
2008 Apr 18
1
spdep question - Moran's I
Dear all,
I would like to calculate a Moran's I statistic using the moran function in the spdep package. The problem I'm having deals with how to create the listw object.
My data stems from the area of social network analysis. I have list of poeple and for each pair of them I have a measure of their relationship strength. So my dataset looks like: Jim; Bob; 0.5
This measure of
2010 Aug 03
2
Collinearity in Moderated Multiple Regression
Dear all,
I have one dependent variable y and two independent variables x1 and x2
which I would like to use to explain y. x1 and x2 are design factors in an
experiment and are not correlated with each other. For example assume that:
x1 <- rbind(1,1,1,2,2,2,3,3,3)
x2 <- rbind(1,2,3,1,2,3,1,2,3)
cor(x1,x2)
The problem is that I do not only want to analyze the effect of x1 and x2 on
y but
2010 Apr 22
1
Convert character string to top levels + NAN
Dear all,
I have several character strings with a high number of different levels.
unique(x) gives me values in the range of 100-200.
This creates problems as I would like to use them as predictors in a coxph
model.
I therefore would like to convert each of these strings to a new string
(x_new).
x_new should be equal to x for the top n categories (i.e. the top n levels
with the highest
2011 May 27
1
Help to improve existing R-Code
Dear all,
I have written a relatively brief R-Code to run a series of simulations.
Currently the code runs for a very long time (up to several days, depending
on the conditions) and I expect this to be the case because it might not be
very efficiently written. I am, for example, relying on several for(...)
loops which could probably be done much faster using a different way of
programming.
I am
2010 Jul 28
1
Time-dependent covariates in survreg function
Dear all,
I'm asking this question again as I didn't get a reply last time:
I'm doing a survival analysis with time-dependent covariates. Until now,
I have used a simple Cox model for this, specifically the coxph function
from the survival library. Now, I would like to try out an accelerated
failure time model with a parametric specification as implemented for
example in the survreg
2011 May 11
1
Total effect of X on Y under presence of interaction effects
Dear all,
this is probably more a statistics question than an R question but probably
there is somebody who can help me nevertheless.
I'm running a regression with four predictors (a, b, c, d) and all their
interaction effects using lm. Based on theory I assume that a influences y
positively. In my output (see below) I see, however, a negative regression
coefficient for a. But several of the
2011 Sep 19
1
Binary optimization problem in R
Dear all,
I would like to solve a problem similar to a multiple knapsack problem and
am looking for a function in R that can help me.
Specifically, my situation is as follows: I have a list of n items which I
would like to allocate to m groups with fixed size. Each item has a certain
profit value and this profit depends on the type of group the item is in. My
problem is to allocate the items
2010 Nov 20
1
txtProgressBar strange behavior in R 2.12.0
Hi,
I am running R 2.12.0 (windows).
example(txtProgressBar)
gives me some funny screen output with all kinds of special characters
appearing and disappearing. It's happening on two different mashines since
vs. 2.12.0. Is this a known issue?
Best,
Jalla
--
View this message in context: http://r.789695.n4.nabble.com/txtProgressBar-strange-behavior-in-R-2-12-0-tp3051976p3051976.html
Sent
2011 Apr 11
1
forest + igraph ?
Hello,
Is it possible to have two meta-plots in one graph (not par(mfrow=c(2,1))? But somthing like
library(metafor)
library("igraph")
if (interactive()) {
forest(dat.Treat$RR, ci.lb=dat.Treat$lower, ci.ub=dat.Treat$upper, xlab="Relative Risk",slab=dat.Treat$ID,refline=1)
forest(dat.Control$RR, ci.lb=dat.Control$lower, ci.ub=dat.Control$upper, xlab="Relative
2011 Feb 20
1
Help Metafor
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2011 Jul 18
1
Extract confidence intervals from rma object (metafor package)
Dear R-experts!
I am working on some meta-analysis using the metafor package. I would like
to extract values of the confidence intervals of the effect sizes of the
single studies from an rma object. Those values are printed out when
plotting a forest plot using the forest function on the rma object, however
I was not able to locate them.
Many thanks for your help!
Jokel
[[alternative HTML
2010 Dec 20
1
Metafor package
I have some question about metafor package.
I'm interest to perform a random effect meta-analysis of proportion
(single group summary of prevalence of disease in a population as
reported by different study)
It ask:
1. "PFT": The Freeman-Tukey double arcsine transformed proportion is
reported to be equal to 1/2*(asin(sqrt(xi/(ni+1))) +
asin(sqrt((xi+1)/(ni+1)))). Hovewer, i
2011 Sep 15
0
Allocation of data points to groups based on membership probabilities
Dear all,
I have a matrix that provides, for a series of data points, the probability
that each of these points belongs to a certain group.
Take the following example, which represents 20 data points and their group
membership probability to five groups (A-E):
set.seed(1)
probs <- matrix(runif(100),nrow=20,