i want to make exponential fitting function

[dlehdgh20]

How can I create a fitting function in LabVIEW similar to the one in the provided origin file?

[altenbach]

Chances are that few people here know how to work with origin files.

Why don't you show us your data and explain what model you want to fit.

The fitting palette has tools for simple exponential fits and for more complicated models you can use nonlinear fitting tools.

For some ideas, have a look at my group.

[dlehdgh20]

I would like to create a fitting function in LabVIEW that fits the data starting from a specific value, similar to the provided shape. I am sharing a sample dataset as a .txt file. I would appreciate it if you could help me create this.

[altenbach]

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@dlehdgh20 wrote:

 starting 

I would like to create a fitting function in LabVIEW that fits the data starting from a specific value, similar to the provided shape. I am sharing a sample dataset as a .txt file. I would appreciate it if you could help me create this.

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OK, this is a double-exponential decay with offset starting at the peak (which is not exactly at t=0 so you might need also a parameter for that unless you can guarantee that t0 is at the right place. Then you also need some criteria what points at negative times and near zero to omit. Obviously, all points to the left don't fit the red line at all. Alternatively, you could use a more complicated model where the left is an exponential rise Or you could set the weight to zero to ignore these points.

Should the program determine what points to omit, do you want to use a cursor to manually select, or do you just want to keep all values that have nonnegative time delay?

Note that your results are truncated and we cannot read the value for y0 (missing the digits after the E). Are you sure that we cannot assume that Y0=0, simplifying the model?

In any case, if you look at some of my examples you should have no problem implementing this as long as you have some basic LabVIEW knowledge. Do you?

[dlehdgh20]

Thank you for your response. It would be great if the program could automatically determine which points to exclude. I'm not sure if assuming y0​=0 to simplify the model is valid. Additionally, in the double-exponential model, it would be helpful to identify the values of the two time constants.

[altenbach]

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@dlehdgh20 wrote:

Additionally, in the double-exponential model, it would be helpful to identify the values of the two time constants.

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Fitting to such a nonlinear model will of course give all best fit parameters. That's the purpose of fitting! What have you tried?

[dlehdgh20]

I have attempted to implement a multiexponential fitting based on your previous explanation. I would like to input specific data values for $x$ and $y$, then write the model function using a formula node so that two decay constants are extracted. However, I am having difficulty with the following:

1. Connecting the specific data values.
2. Writing the model function in the formula node.
3. Ensuring that two decay constants are extracted.
4. What should I do if the data is in the form of a string constant?

[TheWolfmansBrother]

I have no idea if anything i have done here is remotely useful, but i was bored at work, had some time to kill, and saw your post so started screwing around. 

[altenbach]

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@TheWolfmansBrother wrote:

I have no idea if anything i have done here is remotely useful, but i was bored at work, had some time to kill, and saw your post so started screwing around. 

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You did not include the datafile to read. Seems really convoluted.

[TheWolfmansBrother]

They provided a .txt delimited file in a previous post. Thanks for your input.