[R] Why unique(sample) decreases the performance ?

[ufuk beyaztas]

Sorry, the last part of code does not work when uniqu() are used, the true
version;

e <- rnorm(n=50, mean=0, sd=sqrt(0.5625))
x0 <- c(rep(1,50))
x1 <- rnorm(n=50,mean=2,sd=1)
x2 <- rnorm(n=50,mean=2,sd=1)
x3 <- rnorm(n=50,mean=2,sd=1)
x4 <- rnorm(n=50,mean=2,sd=1)
y <- 1+ 2*x1+4*x2+3*x3+2*x4+e
x2[1] = 10     #influential observarion
y[1] = 10      #influential observarion

X <- matrix(c(x0,x1,x2,x3,x4),ncol=5)
Y <- matrix(y,ncol=1)
Design.data <- cbind(X, Y)
 
for (j in 1:nrow(X)) {

result <- vector("list", )

for( i in 1: 3100) {

data <- Design.data[sample(50,50,replace=TRUE),] ##### and
unique(Design.data.....)
dataX <- data[,1:5]
dataY <- data[,6]

B.cap.simulation <- solve(crossprod(dataX)) %*% crossprod(dataX, dataY)
P.simulation <- dataX %*% solve(crossprod(dataX)) %*% t(dataX)
Y.cap.simulation <- P.simulation %*% dataY
e.simulation <- dataY - Y.cap.simulation
dX.simulation <- nrow(dataX) - ncol(dataX)
var.cap.simulation <- crossprod(e.simulation) / (dX.simulation)
ei.simulation <- as.vector(dataY - dataX %*% B.cap.simulation)
pi.simulation <- diag(P.simulation)
var.cap.i.simulation <- (((dX.simulation) *
var.cap.simulation)/(dX.simulation - 1)) -
(ei.simulation^2/((dX.simulation - 1) * (1 - pi.simulation)))
ti.simulation <- ei.simulation / sqrt(var.cap.simulation * (1 -
pi.simulation))
ti.star.simulation <- ei.simulation / sqrt(var.cap.i.simulation * (1 -
pi.simulation))
pi.star.simulation <- pi.simulation + ei.simulation^2 /
crossprod(e.simulation)
WKi.simulation <- (ti.star.simulation)*sqrt(pi.simulation/(1-pi.simulation))
Wi.simulation <- WKi.simulation * sqrt((nrow(dataX)-1)/(1-pi.simulation))

result[[i]] <- list(outWi.simulation=(Wi.simulation),influ.obs = any (dataY
==Y[j,] ))

}

i.obs <- sapply(result,function(x) {x$influ.obs})
ni.result <- result[! i.obs]
ni.Wi.simulation <- sapply(ni.result,function(x) {x$outWi.simulation})
if (j==1) {
ni.Wi.simulation1 <-  ni.Wi.simulation
}else if (j==2) {
ni.Wi.simulation49 <-  ni.Wi.simulation

}else{
ni.Wi.simulation49 <-c(ni.Wi.simulation49, ni.Wi.simulation)
}
} 

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