Linear Regression

I have been asked to compare a daily flow to a linear regression of the previous 8 days. My stats book says that it will require a summation of a series (several greek symbols) and I have not been in that book for almost 20 years.

I am suppose to generate an alarm if the percent difference exceeds a user defined amount.

Could I get some suggestions as how to accomplish this task? Any ladder code would also be appreciated!

It can be done

I have done similar things in the past. You need I suppose a control chart with a standard deviation and Upper and lower control limits.
I would like to give you the formulae needed but I have no idea
how to type in square root or x bar etc. This type of info is available from various web sites. It has to do with quality.
Search for control charts and standard deviation.
As far as programming it in the PLC I don't see it as a problem,
it's just a math.

More Greek letters.

Why don't you just find the standard deviation? Then you can check each day to see how many standard deviations the daily production is from the average production. Using percentanges is bogus.

Also check out confidence intervals. You should see terms like t distributions and degrees of freedom.

In any case I would not do this on a PLC. I would use a spreadsheet.

Phil, I agree with Jiri. I would like to be able to post equations like below simply.



I would like to see integral, differential, sum, subscipts, superscripts, greek letters and PLC symbols of course.

Terry put a lot of effort in to his posts. He also had nice tools. Many of us don't have the time or the tools.

There are some add ins with MS Excel that will preform regression analysis for you. Just goto the add in menu under tools and add the analysis toolpak. should help you figure out the target alarm setpoint