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Not missing at random
2 messages · Blaz Simcic, Dennis Murphy
Hi: Try this: x <- matrix(c(rep(1:5, 9), rep(3, 3), 4), ncol = 7, byrow = TRUE) ## indices of x for which the value is less than 3 candidates <- which(x < 3, arr.ind = TRUE) # generates 18 candidates grabs <- sample(nrow(candidates), 15) # 15/49 ~ 0.3 x2 <- x # copy x x2[candidates[grabs, ]] <- NA x2 HTH, Dennis
On Fri, Jun 3, 2011 at 5:49 AM, Blaz Simcic <blazsimcic at yahoo.com> wrote:
Hello! I would like to sample 30 % of cases (with at least 1 value lower than 3) and among them I want to set all values lower than 3 (within selected cases) as NA (NMAR- Not missing at random). I managed to sample cases, but I don?t know how to set values (lower than 3) as NA. R code: x <- matrix(c(1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,3,3,3,4), ?nrow = 7, ncol=7, byrow=TRUE) ####matrix pMiss <- 30???? ####percent of missing values N <- dim(x)[1]?? ####number of cases candidate<-which(x[,1]<3 | x[,2]<3 | x[,3]<3 | x[,4]<3 | x[,5]<3 | x[,6]<3 | x[,7]<3)??? #### I want to sample all cases with at least 1 value lower than 3, so I have to find candidates idMiss <- sample(candidate, N * p / 100)??? #### I sampled cases Any suggestion? Thanks, Bla? ? ? ? ?[[alternative HTML version deleted]]
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