Beginner Needs Help (Least Squares Analysis

kd001 · 11-03-2009, 04:14 PM

I'm a beginner. I need to create a very basic C program. Basically the program has to perform least square analysis on 8 sets of data. The program needs to read the values (magnitude and velocity) from the keyboard. Magnitude is the x value and logvelocity is the y value. The program does work but its not giving me the correct results. Some help will be much appreciate. I have attached my attempt. Please keep it as simple as possible.

Thanks a lot.

Dino · 11-03-2009, 04:20 PM

I don't see any structure or mechanical errors with the code. Must be a formula issue.

tabstop · 11-03-2009, 04:28 PM

I don't see any formula issues compared to Linear least squares - Wikipedia, the free encyclopedia either at first glance. First thing I would check, you're using "log", which computes ln. If you want to compute log, you need to use "log10".

nonoob · 11-03-2009, 04:31 PM

You are not using the array logv[], but are assigning the logarithm of v[] into y[]...
So maybe it has something to do with that. Formula/correct variable issue.

kd001 · 11-03-2009, 04:35 PM

These are the formulae. For some reason the program is not doing that:

kd001 · 11-03-2009, 04:41 PM

'tabstop' may be onto something. I should calculate log10velocity so when I get the chance I will try changing it to log10.

brewbuck · 11-03-2009, 05:31 PM

Quote:

Originally Posted by kd001

The program does work but its not giving me the correct results.

That's a strange definition of "works."

kd001 · 11-04-2009, 02:51 AM

Quote:

Originally Posted by brewbuck

That's a strange definition of "works."

By works I just meant it compiles and runs.

Anyway changing from log to log10 solved the problem. Thanks to all those who gave their advice.

11-03-2009, 04:14 PM	#1
kd001 Registered User Join Date: Nov 2009 Posts: 4	Beginner Needs Help (Least Squares Analysis I'm a beginner. I need to create a very basic C program. Basically the program has to perform least square analysis on 8 sets of data. The program needs to read the values (magnitude and velocity) from the keyboard. Magnitude is the x value and logvelocity is the y value. The program does work but its not giving me the correct results. Some help will be much appreciate. I have attached my attempt. Please keep it as simple as possible. Thanks a lot. Attached Images
kd001 is offline

11-03-2009, 04:20 PM	#2
Dino Jack of many languages Join Date: Nov 2007 Location: Katy, Texas Posts: 2,070	I don't see any structure or mechanical errors with the code. Must be a formula issue. __________________ Mac and Windows cross platform programmer. Ruby lover.
Dino is offline

11-03-2009, 04:28 PM	#3
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 8,809	I don't see any formula issues compared to Linear least squares - Wikipedia, the free encyclopedia either at first glance. First thing I would check, you're using "log", which computes ln. If you want to compute log, you need to use "log10".
tabstop is offline

11-03-2009, 04:31 PM	#4
nonoob Registered User Join Date: Sep 2008 Location: Toronto, Canada Posts: 521	You are not using the array logv[], but are assigning the logarithm of v[] into y[]... So maybe it has something to do with that. Formula/correct variable issue.
nonoob is offline

11-03-2009, 04:35 PM	#5
kd001 Registered User Join Date: Nov 2009 Posts: 4	These are the formulae. For some reason the program is not doing that: Attached Images Last edited by kd001; 11-03-2009 at 04:37 PM.
kd001 is offline

11-03-2009, 04:41 PM	#6
kd001 Registered User Join Date: Nov 2009 Posts: 4	'tabstop' may be onto something. I should calculate log10velocity so when I get the chance I will try changing it to log10.
kd001 is offline

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