Steve's Junk » freebasic

3 point quadratic regression formula

smackaay — Wed, 29 Apr 2009 22:01:05 +0000

While developing the in-process stormer viscometer, one of my goals is to allow the end user to calibrate the device with 3 fluids of known viscosity. With a bit of help from mathematica, I’ve found the formula and for whoever wants it, it’s posted, also for my own future edification. This formula is meant to convert 3 data points of the form {X1,Y1},{X2,Y2},{X3,Y3} into a form of ax^2+bx+c=y. This is probably the fastest way to do this kind of operation on a microcontroller. Here’s an image of the formula

Reverse Quadratic from data

also, here’s a dirty FreeBasic program using it. regress-3point.bas

Also, for fun I decided to do a cubic version. This is in the form of 4 data points {X1,Y1},{X2,Y2},… converting to ax^3+bx^2+cx+d=y

Cubic equation inverse

You gotta love Mathematica!!!

Temperature and light, several days

smackaay — Thu, 22 Jan 2009 02:41:24 +0000

Well, It’s been a number of days since I built the unit and all’s been tested. Here is a picture of some of the data from my living room over the past several days. The purplish is the temperature and the lighter one is the ambient light. You can see that as the light levels get higher, the furnace stops, thus the temperature stops fluctuating.

The living room temperature as seen over 6 days

Sorry about the small scale of the temperature graph, the graphing program is still a work in progress.

Graphing program and viscometer proceeding apace

smackaay — Wed, 19 Nov 2008 20:50:40 +0000

Well, things are proceeding apace as far as the viscometer is concerned. Unfortunately, the motor is just too non-linear to serve as a useful measuring device. God I’m dumb!

Anyways, my graph-it program is working ok now and producing some useful graphs. I have programmed the save and load features and they seem to work just fine! It will eventually allow for a variety of data analysis techniques.

Here’s a picture of the linearity, or lack thereof.

Reciprocal of motor linearity

The blue at the bottom represents the overall error , the pinkish is the actual reciprocal of the tach values and the brown is the average of the tach values.

Hopefully I can get this working… Sigh!

Writing a new graphing program

smackaay — Wed, 12 Nov 2008 17:06:45 +0000

Since I’m starting to take measurements based on time and value along with multiple data sets, I’ve decided that I need a new graphing program. This one will allow the use of multiple data sets and it will have save files to allow for easy recall of color settings and data parameters. Here are some of the features:

Multiple data sets
Data sets will have options for coloring and graphing choices
New data sets can be derived from existing data sets
Data sets can be compared
More extensive stats will be used

This will all be written in FreeBASIC. Why? Because I like it. Also because FBEdit kicks ass in relation to FBIDE.

Anyways, I’ll post incremental versions.