On Jan 11, 2010, at 10:16 PM, David Winsemius wrote:
On Jan 11, 2010, at 9:38 PM, Márcio Resende wrote:
Hi,
I have a 100x15 matrix and in each row a set of 15 random numbers
out of 25.
for example:
b <- c(1:25)
a <-matrix(0,10,15)
for (i in 1:10){
a[i,] <- sample(b,15,replace = FALSE)
}
I would like to create another matrix (25x100), for example "d"
with the
probability of each number from the first matrix
Therefore I need to track, for example, if number 1 is present in
the first
row (d[1,1]) (which would give me an probability of 1 out of 1).
Then, track again if number 1 is present on the second row (d[2,1])
(And if
not, the probability would be 1 out of 2 = 0.5)...and so on for all
the 25
collumns (25 numbers) and all the 100 rows.
Could anybody help how to do it??
Maybe:
> apply(a, 2, table)[[1]]
1 5 6 7 10 16 21 22 25
1 2 1 1 1 1 1 1 1
> apply(a, 2, table)[[1]]/10
snipped out earlier intermediates
The reason the d matrix looks wrong is that I failed to "zero" it
after an incorrect application of the loop logic. Ignore this column
1. I think the "answer" will be what you asked for.
> for(i in 1:15) {d[as.numeric(names(lapply(apply(a, 2, table), "/",
10)[[i]])), i] <- lapply(apply(a, 2, table), "/", 10)[[i]]}
> d
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[,13] [,14] [,15]
[1,] 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.1 0.0 0.0 0.1
0.1 0.1 0.0 0.0
[2,] 0.1 0.1 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.1
0.0 0.0 0.0 0.0
[3,] 0.1 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.2 0.0
0.1 0.0 0.0 0.0
[4,] 0.1 0.0 0.0 0.2 0.0 0.0 0.2 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.1
[5,] 0.2 0.0 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.3
snip
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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