Hello,
If 60% of the 14 samples come from group C, then 8.4 samples should come
from a group with 6 elements. Do you want sampling with replacement? If
so maybe the following will do.
perc <- c(0.4, 0.6)
tmp <- split(seq_len(nrow(dat)), dat$group == "C")
idx <- sapply(seq_along(tmp), function(i) sample(length(tmp[[i]]),
round(perc[i]*14), replace = TRUE))
idx[[2]] <- idx[[2]] + 16
idx <- unlist(idx)
dat[idx, ]
Hope this helps,
Rui Barradas
Em 07-12-2016 11:58, Marna Wagley escreveu:
Hi R user,
I have samples with covariates for different classes, I wanted to choose
the samples of different groups with different probabilities. For example,
I have a 22 samples size with 3 classes,
groupA has 8 samples
groupB has 8 samples
groupC has 6 samples
I want to select a total 14 samples from 22 samples, in which 40% of the
14 samples should be in groups A and B, 60% of the 14 samples should be in
the group C.
Would you mind to help me on how I can select the samples with that
conditions? I have attached a sample data
dat<-structure(list(sampleID = c(17L, 21L, 36L, 45L, 67L, 82L, 90L,
31L, 70L, 45L, 24L, 80L, 82L, 45L, 85L, 14L, 81L, 96L, 61L, 12L,
65L, 88L), group = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("A",
"B", "C"), class = "factor")), .Names = c("sampleID", "group"
), class = "data.frame", row.names = c(NA, -22L))
thanks,
MW
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