Curve Fittting Express VI

[zubairkhan213]

 hi,

Iam a new bee to LabView.

I want to use Curve Fiiting Express VI  from (Anaylse>> Mathematics>> Curve Fitting >> Curve Fitting). to get the best fit.

The actual formula is : I(L, λ) = Isp(λ)/G(λ) { exp [G(λ) · L ] − 1}

where L is stripe Lenght

I is intensity

lamda is wave lenght

G is the net gain  

given the values of L and I for respective lamda i have to find out the net gain (g) by from the above formula.

the formula which i am using for non linear model is : x/g*(exp(g*l)-1).  is this formula right with respect to the above formula. or shall i change it and i dont know how to use the Curve Fitting Express VI, I will be very much thankful for any kind of advice.

thank you.

[altenbach]

First of all, it is a very bad idea to mix uppercase "I" and lowercase "L" in formulas. In many fonts they look the same, leading to confusion. 😮

It seems you have only one fitting parameter (G). What is Isp? How does your data look like? What is your independent variable?

Are you trying to fit a spectrum or are you just trying to solve a simple formula for one variable (G)?

Sorry, I am a bit confused about your problem. 😉

[zubairkhan213]

Hi altenbach, thank you for your reply.

I(L, λ) = Isp(λ)/G(λ) { exp [G(λ) · L ] − 1} 

i hope the formula is clear now. above formula is taken form Variable Stripe lenght method.

actually i have a very little idea about the formula.

my boss says Isp can be taken as a constant.

G is the net gain (Fitting parameter).

I is the intensity

L is the stripe lenght

i dont know what shall be the independent variable.

my task is related to spectrometer. using a labview vi, i get the data from the ccd camera and store it in a file.

please see the attachment to see how the data looks like

i have to find out netgain(G) using the above data. taking the G values i have to plot a graph. showing the net gain.

i am un aware wheather this can be done using Curve fitting express.vi or shall i derive a formula for G.

if u can give any idea about this problem or show me some way, i will be very much thankfull to you.

bye.

[Andy F.]

I took a stab at this one at this thread:

Solve for G

Hope this helps!
Andy F.

Message Edited by Andy F. on 02-14-2006 04:24 PM