N <- 4 DF <- data.frame(a=1:N, b=1:N) DF[-1,] #nft <- rpois(1,2) nft <- 0 DF[sample(N, N-nft),]
hope this helps. spencer graves
Tord Snall wrote:
Dear all,
As part of a larger function, I am randomly removing rows from a data frame. The number of removed rows is determmined by a Poisson distribution with a low mean. Sometimes, the random number is 0, and that's when the problem starts:
My data frame:
temp
occ x y dbh age 801 0 2977.196 3090.225 6 36.0 802 0 2951.892 3083.769 8 40.6 803 0 2919.111 3075.557 8 40.6 804 0 2914.123 3072.700 9 42.9 805 0 2925.353 3074.675 8 40.6
How many rows (nft) shall be removed?
nft<- rpois(1, 2)[1] 2
nft
Ok remove 2 rows:
temp2<- temp[-sample(nrow(temp), nft), ]
temp2
occ x y dbh age 801 0 2977.196 3090.225 6 36.0 803 0 2919.111 3075.557 8 40.6 805 0 2925.353 3074.675 8 40.6
No problem.
However, sometimes rpois(1, 2) lead to nft=0, and in that case I do not want
temp2<- temp[-sample(nrow(temp), 0), ][1] occ x y dbh age
temp2
<0 rows> (or 0-length row.names)
Instead I want
temp2<- temp
temp2
occ x y dbh age 801 0 2977.196 3090.225 6 36.0 802 0 2951.892 3083.769 8 40.6 803 0 2919.111 3075.557 8 40.6 804 0 2914.123 3072.700 9 42.9 805 0 2925.353 3074.675 8 40.6
Could someone help whith that?
Thanks in advance!
Sincerely, Tord
----------------------------------------------------------------------- Tord Sn�ll Avd. f v�xtekologi, Evolutionsbiologiskt centrum, Uppsala universitet Dept. of Plant Ecology, Evolutionary Biology Centre, Uppsala University Villav�gen 14 SE-752 36 Uppsala, Sweden Tel: 018-471 28 82 (int +46 18 471 28 82) (work) Tel: 018-25 71 33 (int +46 18 25 71 33) (home) Fax: 018-55 34 19 (int +46 18 55 34 19) (work) E-mail: [EMAIL PROTECTED] Check this: http://www.vaxtbio.uu.se/resfold/snall.htm!
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