# [R] Problem about for loop

Martyn Byng Martyn.Byng at nag.co.uk
Mon Jan 17 15:47:46 CET 2011

```Hi,

Looks like the function "theta" takes a variable "data", but that
variable is not being used in the body of the function (you are using
the global dataX and dataY, which will be the same each time the
function is called).

Martyn

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of ufuk beyaztas
Sent: 17 January 2011 13:21
To: r-help at r-project.org
Subject: [R] Problem about for loop

Hi everyones, my function like;

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

data.x <- matrix(c(x0,x1,x2,x3,x4),ncol=5)
data.y <- matrix(y,ncol=1)
data.k <- cbind(data.x,data.y)
dataX <- data.k[,1:5]
dataY <- data.k[,6]

theta <- function(data) {
B.cap <- solve(crossprod(dataX)) %*% crossprod(dataX,dataY)
P <- dataX %*% solve(crossprod(dataX)) %*% t(dataX)
Y.cap <- P %*% dataY
e <- dataY - Y.cap
dX <- nrow(dataX) - ncol(dataX)
var.cap <- crossprod(e) / (dX)
ei <- as.vector(dataY - dataX %*% B.cap)
pi <- diag(P)
var.cap.i <- (((dX) * var.cap) / (dX - 1)) -
(ei^2 / ((dX-1) * (1 - pi)))
ti <- ei / sqrt(var.cap * (1 - pi))
Ci <- (ti^2 / (ncol(dataX))) * (pi / (1 - pi))
output.i <- mean(Ci)}

result <- list()

for ( i in 1:5){

data <- replicate(1, data.k[sample(50,50,replace=T),], simplify = FALSE)

output.j <- theta(data)

result <- c(result,(list(output.j))) }
table <- do.call(rbind.data.frame,result)
names(table)=c("cooks")
table

This function give same results each time, the data is changing every
time
but mean(Ci)s are always same.
Does anyone have an idea about how to be? Thanks for any idea

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