Displaying 20 results from an estimated 11000 matches similar to: "Converting a character string into an object variable"
2006 Oct 31
3
Missing data analysis in R
I am looking for a book that discusses the theory of multiple imputation
(and other methods of dealing with missing data) and, just as
importantly, how to implement these methods in R or S-Plus. Ideally,
the book would have a structure similar to Faraway (Regression),
Pinheiro&Bates (Mixed Effects) and Wood (GAMs) and would be very modern
(i.e. published within the last couple of years).
2007 Jan 12
7
Making TIFF images with rtiff
Many medical journals and publishers require that images, whether
photographs or line art, be submitted as high resolution .TIFF images.
One option for R users is to produce an image in one format and to
convert it to a .TIFF file using a second software program. My
experience has been that this option often results in images of poorer
quality, often with blurry contours, and a loss of
2007 Mar 13
1
Freeman-Tukey arcsine transformation
R-Experts:
Does anyone know if there are R functions to perform the Freeman-Tukey
double arcsine transformation and then backtransform it?
Thanks,
Brant Inman
Mayo Clinic
2008 Jan 21
3
'matrix' returns integer instead of decimal
R-helpers:
I am experiencing some odd behavior with the 'matrix' function that I have
not experienced before and was wondering if there is something that I was
missing in my code.
---------------------------------
> sessionInfo()
R version 2.6.1 (2007-11-26)
i386-pc-mingw32
locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MONETARY=English_United
2007 Apr 25
1
prelim.norm() function not working
R-experts:
I am trying to reproduce some of Paul Allison's results in his little
green book on missing data (Sage 2002). The dataset for which I am
having problems, "usnews", can be found at:
http://www.ats.ucla.edu/stat/books/md/default.htm. I am working on a
Windows machine with R 2.5 installed, all packages up-to-date.
The problem has to do with the prelim.norm() function of the
2006 Oct 27
1
Censored Brier Score and Royston/Sauerbrei's D
System: R 2.3.1 on a Windows XP computer.
I am validating several cancer prognostic models that have been
published with a large independent dataset. Some of the models report a
probability of survival at a specified timepoint, usually at 5 and 10
years. Others report only the linear predictor of the Cox model.
I have used Harrell's c index for censored data (rcorr.cens) as a
measure of
2007 Apr 20
3
Opinion on R plots: connecting X and Y
Attention R users, especially those that are experienced enough to be
opinionated, I need your input.
Consider the following simple plot:
x <- rnorm(100)
y <- rnorm(100)
plot(x, y, bty='n')
A colleague (and dreaded SAS user) commented that she thought that my
plots could be "cleaned up" by connecting the X and Y axes. I know that
I can do that with bty='l' but I
2007 Mar 05
3
Mixed effects multinomial regression and meta-analysis
R Experts:
I am conducting a meta-analysis where the effect measures to be pooled
are simple proportions. For example, consider this data from
Fleiss/Levin/Paik's Statistical methods for rates and proportions (2003,
p189) on smokers:
Study N Event P(Event)
1 86 83 0.965
2 93 90 0.968
3 136 129 0.949
4 82 70 0.854
Total
2007 May 17
1
MICE for Cox model
R-helpers:
I have a dataset that has 168 subjects and 12 variables. Some of the
variables have missing data and I want to use the multiple imputation
capabilities of the "mice" package to address the missing data. Given
that mice only supports linear models and generalized linear models (via
the lm.mids and glm.mids functions) and that I need to fit Cox models, I
followed the previous
2006 Nov 13
3
Profile confidence intervals and LR chi-square test
System: R 2.3.1 on Windows XP machine.
I am building a logistic regression model for a sample of 100 cases in
dataframe "d", in which there are 3 binary covariates: x1, x2 and x3.
----------------
> summary(d)
y x1 x2 x3
0:54 0:50 0:64 0:78
1:46 1:50 1:36 1:22
> fit <- glm(y ~ x1 + x2 + x3, data=d, family=binomial(link=logit))
>
2011 Feb 28
3
Measuring correlations in repeated measures data
R-helpers:
I would like to measure the correlation coefficient between the repeated measures of a single variable that is measured over time and is unbalanced. As an example, consider the Orthodont dataset from package nlme, where the model is:
fit <- lmer(distance ~ age + (1 | Subject), data=Orthodont)
I would like to measure the correlation b/t the variable "distance" at
2006 Nov 03
6
Import problem with S-Plus 7.0 dataset
I am running R 2.3.1 on a Windows XP machine. I am trying to import
some data into R that is stored as an S-Plus 7.0 .sdd file.
When I run the following command, I get this error:
> library(foreign)
> d <- read.S(file='H:\\Research\\data.sdd')
Error in read.S(file = "H:\\Research\\data.sdd") :
not an S object
The dataset is fairly large, roughly 13000 rows
2006 Nov 03
6
Import problem with S-Plus 7.0 dataset
I am running R 2.3.1 on a Windows XP machine. I am trying to import
some data into R that is stored as an S-Plus 7.0 .sdd file.
When I run the following command, I get this error:
> library(foreign)
> d <- read.S(file='H:\\Research\\data.sdd')
Error in read.S(file = "H:\\Research\\data.sdd") :
not an S object
The dataset is fairly large, roughly 13000 rows
2007 Apr 12
3
Putting 2 breaks on Y axis
R plotting experts:
I have a bivariate dataset composed of 300 (x,y) continuous datapoints.
297 of these points are located within the y range of [0,10], while 2
are located at 20 and one at 55. No coding errors, real outliers.
When plotting these data with a scatterplot, I obviously have a problem.
If I plot the full dataset with ylim = c(0,55), then I cannot see the
structure in the data in
2007 Jan 06
2
Using VGAM's vglm function for ordinal logistic regression
R-Experts:
I am using the vglm function of the VGAM library to perform proportional
odds ordinal logistic regression. The issue that I would like help with
concerns the format in which the response variable must be provided for
this function to work correctly. Consider the following example:
------
library(VGAM)
library(MASS)
attach(pneumo)
pneumo # Inspect the format of the original dataset
2007 Jan 05
1
Calling "confint.glm" from within another function
On July 12, 2004 Spencer Graves wrote an email describing essentially
the same issue that I would like help on: calling the confint function
from within another homemade function. Because he provided many good
examples of the problem, I will not reproduce them here but will instead
refer readers to the original posting:
http://www.mail-archive.com/r-help at stat.math.ethz.ch/msg23826.html
It is
2011 Jan 17
1
Replacing rows in a data frame
R-helpers,
Below is a simple example of some output that I am getting while trying to work with a data frame in R 2.12.1 for Mac.
-----
> testdat <- data.frame(matrix(ncol=10, nrow=10))
> colnames(testdat) <- c('a','b','c','d','e','f','g','h','i','j')
> testdat[seq(1,10,3),] <-
2010 Nov 17
1
Error: package 'pcvsuite' was built before R 2.10.0: please re-install it
R-helpers,
I have had difficulty installing the "pcvsuite" package on R version 2.12.0 (2010-10-15). The pcvsuite package is not available on CRAN, but is located for download at the following website at the University of Washington:
Windows version
http://labs.fhcrc.org/pepe/dabs/pcvsuite_1.0.zip
Mac version
2007 Apr 20
2
Using power.t.test over a range of conditions
R-Helpers:
I would like to perform sample size calculations for an experiment. As
part of this process, I would like to know how various assumptions
affect the sample size calculation. For instance, one thing that I
would like to know is how the calculated sample size changes as I vary
the difference that I would like to detect. I tried the following
first, but got the associated error
2007 May 02
1
? R 2.5.0 alpha bug
This email is intended to highlight 2 problems that I encountered
running R 2.5.0 alpha on a Windows XP machine.
#1 - Open script error
If I click the "Open folder" icon on the toolbar, R opens my script
files perfectly. However, when I select "File > Open Script >
MyFileLocation", I get a fatal error that causes R to close immediately.
This error was reproduced on 3