> DF <- data.frame(a=1:2, b=c(0,0)) > DFzeros <- sapply(DF, function(x)all(x==0)) > names(DF)[!DFzeros] [1] "a"
hope this helps. spencer graves
Jeff D. Hamann wrote:
Hi R-Wizards:
I've looking through the R docs and have yet to find what I'm looking for and have tried a few intermediate steps to now avail yet and rather than spend another few hours looking for the solution, I figured I would post a message.
I have a matrix (actually a set of them) that I want to pull all the names of the non-zero columns into a vector/list for further processing:
d0 d1 d2 s0 s1 s2 s3 [1,] -4.4721360 -447.29878969 -436.18978037 0 0 0 0 [2,] 0.2236068 -25.83121172 -29.21571675 0 0 0 0 [3,] 0.2236068 0.13009088 42.49338060 0 0 0 0 [4,] 0.2236068 0.17155235 0.04891280 0 0 0 0 [5,] 0.2236068 -0.08027479 -0.14749423 0 0 0 0 [6,] 0.2236068 -0.02394758 -0.12845820 0 0 0 0 [7,] 0.2236068 0.03838012 -0.15270556 0 0 0 0 [8,] 0.2236068 0.18150155 -0.17073267 0 0 0 0 [9,] 0.2236068 -0.14047328 -0.11013806 0 0 0 0 [10,] 0.2236068 -0.34247697 -0.05627832 0 0 0 0 [11,] 0.2236068 -0.27058719 0.31379811 0 0 0 0 [12,] 0.2236068 -0.04930450 0.41093718 0 0 0 0 [13,] 0.2236068 0.10968920 0.32996356 0 0 0 0 [14,] 0.2236068 -0.05104658 0.08743581 0 0 0 0 [15,] 0.2236068 -0.19184524 -0.29548841 0 0 0 0 [16,] 0.2236068 -0.06285400 -0.26123732 0 0 0 0 [17,] 0.2236068 -0.52558878 -0.34821174 0 0 0 0 [18,] 0.2236068 0.15258305 -0.10895070 0 0 0 0 [19,] 0.2236068 0.22044668 -0.21442723 0 0 0 0 [20,] 0.2236068 0.51934865 -0.41193918 0 0 0 0
such that I only end up with a list of names (d0,d1,d2). I've been using the qr( x )$rank to get the number of non-zero columns, but I'm not sure how to only return the names of the non-zero columns as
colnames( qr( attr( eval( nlsystemols$eq[[1]]$deriv ), "gradient" ) )$qr )
will return
[1] "d0" "d1" "d2" "s0" "s1" "s2" "s3"
Is/Are there one of those great S or R function/shortcuts that will return a submatrix(?) or a partioned matrix such that when I call colnames() I get:
[1] "d0" "d1" "d2"
Thanks, Jeff.
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