Dear list;
I just created a utility function that replicates what I have done in
the past with Excel or OO.org by putting a formula of the form
=sum($A1:A$1) in an upper-corner of a section and then doing a "fill"
procedure by dragging the lower-rt corner down and to the right. When
divided by the grand sum of the entries this function then calculates
a 2D-discrete-ECDF.
I keep thinking I am missing the obvious, but I did try searching.
Here is my effort at creating that functionality:
ecdf.tbl <- function (.dat) { .dat <- data.matrix(.dat) #speeds up
calculations
.sdat <- matrix(0, nrow(.dat), ncol(.dat) )
.sdat[] <- sapply(1:ncol(.dat), function(x)
sapply(1:nrow(.dat),
function(y) sum(.dat[1:y, 1:x],
na.rm=TRUE ) ) )
return(.sdat) }
> tst <- read.table(textConnection("NA 5 6
4 5 7
5 6 8
6 7 9
NA 8 NA") )
> tst
V1 V2 V3
1 NA 5 6
2 4 5 7
3 5 6 8
4 6 7 9
5 NA 8 NA
> ecdf.tbl(tst)
[,1] [,2] [,3]
[1,] 0 5 11
[2,] 4 14 27
[3,] 9 25 46
[4,] 15 38 68
[5,] 15 46 76
> ecdf.tbl(tst)/sum(tst, na.rm=TRUE)
[,1] [,2] [,3]
[1,] 0.00000000 0.06578947 0.1447368
[2,] 0.05263158 0.18421053 0.3552632
[3,] 0.11842105 0.32894737 0.6052632
[4,] 0.19736842 0.50000000 0.8947368
[5,] 0.19736842 0.60526316 1.0000000
Did I miss a more compact vectorized or sweep()-ed solution? (I
realize this is not really a function in the sense that ecdf() is.) I
have seen prop.table and margin.table, but could not see how they
would address this problem.
--
David Winsemius, MD
West Hartford, CT
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