In this post I take a closer look at the different model types that are available to support curve fitting.
The JMP scripting language has a number of convenient functions for handling files external to JMP. Here’s an example:
// purge the temporary folder
files = filesIndirectory(tmpDir);
path = convertFilePath(files[i],base(tmpDir));
Code folding allows you to collapse a block of code – you can use it to focus on high-level structure without getting lost in the detail.
To enable code folding enable to option under the Script Editor section of Preferences, found under the File menu.
I use it with my user-defined functions to give me an overview of contents within an include file. Combined with appropriately placed comments this helps to summarise the contents of a library of functions. Here is an example:
Process capability is a well-established technique for evaluating the degree to which a process is capable of delivering a product within specification. But what if the specifications are unknown or at best tentative?
The calculations of process capability analysis can be reversed so that for a given set of target capability values the associated specification limits can be generated. The calculation is straight-forward for a normal distribution but needs a bit more thought when it comes to asymmetric distributions.
The lognormal distribution is a commonly used distribution for modelling asymmetric data. It’s just the log of a Normal distribution right? Well no, it’s actually the other way around. You take the log of a lognormal distribution to arrive at a normal distribution. Is it just me, but I always have a bit of a mental block about this, it always feels a bit back to front.
In this post I will explore the relationship between a lognormal distribution and a normal distribution.
In my last post I introduced the idea of using the JSL script editor as a simple command line calculator; and prior to that I discussed how process capability indices (Cp,Cpk) are a convenient shorthand notation but suffer from lack of transparency. Today I will bring these two themes together by showing how I can use the JSL script editor to calculate defective parts per million (dppm) for a given set of capability indices Cp and Cpk.