R- Help (looping)

Ok,

This really helped.

You've probably noticed, I'm a begginer using R.

And when you said that you tried with rnorm and the counts were not zero,
where did you use the rnorm?

The point is, I need this count to be different from zero, so I can use the
ARL later on.

I need how many values are out of control (for each column /variable),
store these values in a vector, calculate this vector's mean, and then
calculate the ARL.

I've got to the same point as you did, but I'm stuck in the same problem. I
need this count do be different from zero.

I'm still learning, haha, please be patient.

Best Regards.

2012/7/30 Rui Barradas <ruipbarradas at sapo.pt>

Hello,

Try the following.

# make up some data
dds <- 1e3
nc <- 10
xss <- data.frame(matrix(runif(nc***dds, min=-1, max=1), ncol=nc))
names(xss) <- paste0("xs", 1:10)

# two functions with descriptive names
getControlLimits <- function(x, L = 3){
     mu <- mean(x)
     sigma <- sd(x)
     c(lcl = mu - L*sigma, ucl = mu + L*sigma)
}

countOutOfControl <- function(x, L = 3){
     cl <- getControlLimits(x, L = L)
     sum( x < cl["lcl"] | x > cl["ucl"] )
}

sapply(xss, getControlLimits)    # To know why the next returns all zeros
sapply(xss, countOutOfControl)    # No values outside control limits


The data comes from an uniform in the interval (-1, 1) therefore the sd is
sqrt(1/3) = 0.577. Times 3 gives values for lcl and ucl clearly below and
above -1 and 1, respectively.  (I've tried rnorm and the counts were not
zero.)
But this is just a data example to see if the code works, and it does.


Hope this helps,

Rui Barradas

Em 30-07-2012 22:04, Wellington Silva escreveu:

Ok Rui,

I'll try to explain myself a little bit better.

I have 10 columns, with 1000 rows each. (Each column represents a variable
of the process)

these columns were simulated using runif, with values between 4 and 6.

I need to calculate the control limits for each column (variable), and
verify if they are within the bounds accepted.

For now, I'm reading these columns separately, I'm creating variables to
read only one of the each column, and then check if the values in this
column is within the limits or not.

PS. All these columns originally come from a dataframe. something like
this: (dds = 1000)

xs1<-runif(dds, min=-1, max=1)
xs2<-runif(dds, min=-1, max=1)
xs3<-runif(dds, min=-1, max=1)
xs4<-runif(dds, min=-1, max=1)
xs5<-runif(dds, min=-1, max=1)
...
xs10<-runif(dds, min=-1,max=1)
xs<-data.frame(xs1,xs2,xs3,**xs4,xs5,..xs10)