| Author |
 Topic  |
|
|
luke419
Albania
Posts |
 Posted - 01/13/2009 : 07:42:00 AM
|
Origin Ver.: 8.0
Operating System: Windows XP
I'd like to fit parabolic like data which pass the origin
point with not built-in parabolic function (y = A + B*x + C*x^2) but user defined function of y = A * x^2.
Hence, I made user-defined function of y = A * x^2.
The detail of it is as follows.
Parameter Settings
InitialValues = --(V)
Meanings = ?
LowerBounds = --(X, OFF)
UpperBounds = --(X, OFF)
NamingMethod = User-Defined
NumberOfSignificantDigits =
Enable Auto initialization: unchecked
Use OriginC: unchecked
However, it fails to give a normal fitting result.
the result is as follows.
Model quadratic (User)
Equation y = A * x^2
Reduced Chi-Sqr 0
Adj. R-Square 0
Value Standard Error
?$OP:F=1 A -- --
What's wrong with it?
What should I do for it?
With best regards,
|
|
|
scunque
5 Posts |
Posted - 01/13/2009 : 11:47:04 AM
|
Why not use Allometric1 in the Power category? You can set the b parameter to fixed value of 2 then the equation becomes
y=a*x^2 |
 |
|
|
luke419
Albania
Posts |
Posted - 01/14/2009 : 06:03:13 AM
|
Thanks a lot for the answer.
In spite of a good working of it, I'd like to know how I can utilize user-defined function, too.
Is it not so easy?
How can I use it in detail?
Best wishes,
|
|
|
|
greg
USA
1379 Posts |
Posted - 01/15/2009 : 11:12:04 AM
|
If your Function definition is indeed
y = A * x^2
and your Independent Variable is x (case important if using OriginC)
and your Dependent Variable is y (case important if using OriginC)
and Parameter Name is A (case important if using OriginC)
and you have some form of Parameter Initialization, like
A=1;
then your function should work. If it doesn't, send the FDF file to tech@originlab.com and they will tell you what's wrong. |
|
|
| |
Topic |
|
|
|
user defined function for fitting of data