Matrix Completion 2

X <- data.matrix(scale(USArrests))

nomit <- 20
set.seed(15)
ina <- sample(seq(50), nomit)
inb <- sample(1:4, nomit, replace = TRUE)
Xna <- X
index.na <- cbind(ina, inb)
Xna[index.na] <- NA

fit.svd <- function(X, M = 1) {
  svdob <- svd(X)
  with(svdob,
       u[, 1:M, drop = FALSE] %*%
         (d[1:M] * t(v[, 1:M, drop = FALSE]))
  )
}

Xhat <- Xna
xbar <- colMeans(Xna, na.rm = TRUE)
Xhat[index.na] <- xbar[inb]

thresh <- 1e-7
rel_err <- 1
iter <- 0
ismiss <- is.na(Xna)
mssold <- mean((scale(Xna, xbar, FALSE)[!ismiss])^2)
mss0 <- mean(Xna[!ismiss]^2)

while(rel_err > thresh) {
  iter <- iter + 1
  # Step 2(a)
  ...
  # Step 2(b)
  ...
  # Step 2(c)
  ...
  cat("Iter:", iter, "MSS:", mss, "Rel. Err:", rel_err, "\n")
}

Je kunt zo vaak indienen als je wenst. Er wordt enkel rekening gehouden met je laatst ingediende oplossing.