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,
Blaž
	[[alternative HTML version deleted]]

