On Feb 4, 2011, at 4:24 PM, Mcmahon, Kwyatt wrote:
Hello compadRes,
I'm developing a script that selects "cells" over a certain
metabolic rate to kill them. A rate between 9 and 12 means that the
cells are candidates for death.
I'll show you what I mean:
# a would be a vector of cell metabolic rates.
a<-c(8, 7, 9, 6, 10, 11, 4, 5, 6)
#now identify which cells will be candidates for death, namely those
cells with metabolic rates>9
b<-a[a>6]
#This would select all cells with rates >6
rbinom(length(b), size=1, prob=1)
No, you have an overly complex way of generating a vector of all 1's
with length(b). And it's not clear what you mean by "select". I see no
caode that would do any selection or indexing.
#This will select cells using a an exponential probability
distribution
rbinom(length(b), size=1, prob=(seq(0, 1, by=0.1)^2))
Again no selection appears to be taking place.
I have two questions:
1) Am I correct in my interpretations?
2) I'd actually like to have this probability scaled so that
cells with rates of 9 are unlikely to be selected and those near 12
are highly likely. How can I code this?
a[ sample(1:length(a), prob=0.1+(a>9) ,replace=TRUE) ]
[1] 10 10 11 10 10 11 10 11 10
> a[sample(1:length(a), prob=0.1+(a>9) ,replace=TRUE) ]
[1] 10 10 11 11 11 11 5 10 10
The "rates" over 9 are 11 times (= 1.1/0.1) as likely to be selected.
You can adjust the ratio by altering the 0.1 value."+" with the first
argument numeric act to coerce the logical vector to 1's and 0's.
--
David.
Thanks in advance,
Wyatt
sessionInfo()
R version 2.11.1 (2010-05-31)
i386-pc-mingw32
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_2.11.1
K. Wyatt McMahon, Ph.D.
Postdoctoral Research Associate
Department of Internal Medicine
3601 4th St. - Lubbock, TX - 79430
P: 806-743-4072
F: 806-743-3148
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