sessionInfo()R version 2.15.2 (2012-10-26)
Platform: i686-pc-linux-gnu (32-bit)
locale:
[1] LC_CTYPE=en_GB.UTF-8 LC_NUMERIC=C
LC_TIME=en_GB.UTF-8
[4] LC_COLLATE=en_GB.UTF-8 LC_MONETARY=en_GB.UTF-8
LC_MESSAGES=en_GB.UTF-8
[7] LC_PAPER=C LC_NAME=C
LC_ADDRESS=C
[10] LC_TELEPHONE=C LC_MEASUREMENT=en_GB.UTF-8
LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] boot_1.3-7
loaded via a namespace (and not attached):
[1] tools_2.15.2
Hello. I have a very straightforward question. Here's some simulated data
(N=500)
test<-data.frame(A=rnorm(500,mean=2.72,sd=5.36),
B=sample(c(12,20,24,28,32),size=500,prob=c(0.333,0.026,0.026,0.436,0.179),replace=TRUE),C=sample(c(0,1),size=500,replace=TRUE),D=sample(c(0,1),size=500,replace=TRUE))
head(test) A B C D
1 1.181804 28 1 0
2 -5.602307 12 1 1
3 2.925090 24 1 1
4 3.437408 28 1 0
5 -6.503531 32 0 0
6 11.013888 12 1 1
which I then bootstrap using
library(boot)
bs <- function(formula, data, indices) { test <- data[indices,]
fit <- lm(formula, data=test) return(coef(fit))
}
The following works
results <- boot(data=test, statistic=bs, R=1000, A~B+C+D+C*D)
results
But when I then amend the dataset by changing the D variable to simulate
fixed proportions
D=sample(c(0,1),size=500,prob=c(0.564,0.436),replace=TRUE
head(test) A B C D
1 5.73771963 28 0 1
2 -0.19040750 12 1 0
3 2.22515982 12 0 1
4 -0.02905223 32 1 0
5 4.68314112 28 0 1
6 5.10711732 12 1 0
the same bootstrapping routine chokes with an error
results <- boot(data=test, statistic=bs, R=1000, A~B+C+C*D)Error in
data[indices, ] : incorrect number of dimensions
despite the fact that the B variable also has simulated fixed proportions
and yet the original code ran without any errors. I have two general
observations to make about this:
(1) this does not make sense; and
(2) I don't understand this.
How best to make these two observations go away and run the code to my
satisfaction?
Many thanks.
--
Clive Nicholas (clivenicholas.posterous.com)
[Please DO NOT mail me personally here, but at <clivenicho...@hotmail.com>.
Please respond to contributions I make in a list thread here. Thanks!]
"My colleagues in the social sciences talk a great deal about methodology.
I prefer to call it style." -- Freeman J. Dyson
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