Setting custom LCL and UCL limits with qcc (Rstudio)

Question

Perhaps this is an easy question but I am quite new wirh R and am struggling to define custom UCL and LCL limits in xBar control charts. In productions we have already set tollerances that must be fulfilled and I would like to set the limits (LCL and UCL) according the tollerances but I do not know how to do.

I write here a simple example to better understand:

library(qcc)
data(pistonrings)
diameter <- pistonrings$diameter
q1 <- qcc(diameter, type = "xbar.one", plot = TRUE)

This creates the xBar chart defining the two limits according the measurements and confidence interval. I would like to set them as following (just as example) and calculate the results according these values:

LCL: 73.99
UCL: 74.02

Is it possible?

Answer 1

I fixed the issue. It was enough specifying the limits with the qcc function:

q1 <- qcc(diameter, type = "xbar.one", plot = TRUE, limits = c(73.99,74.02))