Engine Works
Under the hood of Alteryx: tips, tricks and how-tos.
I got asked the question of how to generate random numbers with a normal distribution. A quick search online provides all kinds of formulas, it is a simple matter of picking one to implement. I could of course implement this in the formula library in C++, but that doesn't provide instant gratification, so off writing a macro I go. Some of the functions are iterative, which would be slower and more difficult in Alteryx, so I chose a simpler formula. The formulas online also produce a normal distribution with and average of 0 and a standard deviation of 1. Depending on the data you are trying to model, you probably want to change that. Rather than make the use do it, I added some parameters in the macro.
Finally, anytime you write a macro it is nice to test it. I wrote a quick module to generate 1,000,000 random #'s and test their average, StdDev, and also produce a chart so you can visually confirm that it is a norm distribution.
The results of that are:
Number of Iterations Tested: 1,000,000
Average(should be close to 100): 100.02
Standard Deviation (should be close to 15): 14.98
My favorite part of this is I used the chart that the test module produced as the icon for the macro. Kind of recursive. Anyway, now generating random numbers with a Gaussian Distribution is as easy as dragging out a macro. The macro and test module can be found here.
