pkg/R/sampleIO.R

   1 #' Generate sample inputs-outputs
   2 #'
   3 #' Generate input matrix X of size nxd and binary output of size n, where Y is subdivided
   4 #' into K groups of proportions p. Inside one group, the probability law P(Y=1) is
   5 #' described by the corresponding column parameter in the matrix β + intercept b.
   6 #'
   7 #' @param n Number of individuals
   8 #' @param p Vector of K-1 populations relative proportions (sum <= 1)
   9 #' @param β Vectors of model parameters for each population, of size dxK
  10 #' @param b Vector of intercept values (use rep(0,K) for no intercept)
  11 #' @param link Link type; "logit" or "probit"
  12 #'
  13 #' @return A list with
  14 #' \itemize{
  15 #'   \item{X: the input matrix (size nxd)}
  16 #'   \item{Y: the output vector (size n)}
  17 #'   \item{index: the population index (in 1:K) for each row in X}
  18 #' }
  19 #'
  20 #' @export
  21 generateSampleIO = function(n, p, β, b, link)
  22 {
  23     # Check arguments
  24     tryCatch({n = as.integer(n)}, error=function(e) stop("Cannot convert n to integer"))
  25     if (length(n) > 1)
  26         warning("n is a vector but should be scalar: only first element used")
  27     if (n <= 0)
  28         stop("n: positive integer")
  29     if (!is.matrix(β) || !is.numeric(β) || any(is.na(β)))
  30         stop("β: real matrix, no NAs")
  31     K = ncol(β)
  32     if (!is.numeric(p) || length(p)!=K-1 || any(is.na(p)) || any(p<0) || sum(p) > 1)
  33         stop("p: positive vector of size K-1, no NA, sum<=1")
  34     p <- c(p, 1-sum(p))
  35     if (!is.numeric(b) || length(b)!=K || any(is.na(b)))
  36         stop("b: real vector of size K, no NA")
  37
  38     #random generation of the size of each population in X~Y (unordered)
  39     classes = rmultinom(1, n, p)
  40
  41     d = nrow(β)
  42     zero_mean = rep(0,d)
  43     id_sigma = diag(rep(1,d))
  44     # Always consider an intercept (use b=0 for none)
  45     d = d + 1
  46     β = rbind(β, b)
  47     X = matrix(nrow=0, ncol=d)
  48     Y = c()
  49     index = c()
  50     for (i in 1:ncol(β))
  51     {
  52         index = c(index, rep(i, classes[i]))
  53         newXblock = cbind( MASS::mvrnorm(classes[i], zero_mean, id_sigma), 1 )
  54         arg_link = newXblock%*%β[,i]
  55         probas =
  56             if (link == "logit")
  57             {
  58                 e_arg_link = exp(arg_link)
  59                 e_arg_link / (1 + e_arg_link)
  60             }
  61             else #"probit"
  62                 pnorm(arg_link)
  63         probas[is.nan(probas)] = 1 #overflow of exp(x)
  64         X = rbind(X, newXblock)
  65         Y = c( Y, vapply(probas, function(p) (rbinom(1,1,p)), 1) )
  66     }
  67     shuffle = sample(n)
  68     # Returned X should not contain an intercept column (it's an argument of estimation
  69     # methods)
  70     list("X"=X[shuffle,-d], "Y"=Y[shuffle], "index"=index[shuffle])
  71 }