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Help fitting and selecting data?

Soumyaranjan Jhankar, MPI FKF
Posted 2 years ago

Kindly find the data:
https://drive.google.com/file/d/1Zw_GBnhFYbEglEKzTXnCv4o5xEMMT9n1/view?usp=sharing

I want to fit my data. After using drop and select, I am getting blank {}. I want to fit my data of XZ Plane and potential. Kindly help, as soon as possible
POSTED BY: Soumyaranjan Jhankar
7 Replies
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Rohit Namjoshi
Rohit Namjoshi
Posted 2 years ago

Something like this?

(* MinMax for x, y, z, p *)
MinMax /@ Transpose@DataxyzStein
(* {{-0.495, 0.495}, {-0.495, 0.495}, {-0.305, 0.305}, {0.299106, 0.998006}} *)

(* Select positive x values *)
DataxzSteinPosX = Select[DataxzStein, #[[1]] >= 0 &]

MinMax /@ Transpose@DataxzSteinPosX
(* {{0.005, 0.495}, {-0.305, 0.305}, {0.302262, 0.998001}} *)
POSTED BY: Rohit Namjoshi

I mean to say. I want to command Mathematica that Please select data points with a range from ( -0.32 to +0.32) for x column(1st), a range from ( -0.22 to +0.22) for z column (3rd) along with its corresponding potential data in the 4th columns. Then I will use those data points for fitting.
POSTED BY: Soumyaranjan Jhankar
Rohit Namjoshi
Rohit Namjoshi
Posted 2 years ago

Add whatever filtering on values you want

(* In DataxzStein, x is column 1 and z is column 2 *)
DataxzSteinSubset = 
 Select[DataxzStein, Between[#[[1]], {-0.32, 0.32}] && Between[#[[2]], {-0.22, 0.22}] &] 

MinMax /@ Transpose@DataxzSteinSubset
(* {{-0.315, 0.315}, {-0.215, 0.215}, {0.447852, 0.889891}} *)

Use DataxzSteinSubset to fit.
POSTED BY: Rohit Namjoshi
Rohit Namjoshi
Rohit Namjoshi
Posted 2 years ago

Extract columns 1, 3, 4

DataxzStein = DataxyzStein[[All, {1, 3, 4}]]

FittXZStein = 
  NonlinearModelFit[
   DataxzStein, {ModelxzStein}, {Subscript[T, 0], Subscript[T, 2], 
    Subscript[T, 4], Subscript[T, 6], Subscript[T, 8], Subscript[T, 10]}, {x, z}]

FittXZStein["RSquared"]
(* 0.9845 *)

FittXZStein["ParameterTable"]

enter image description here
POSTED BY: Rohit Namjoshi

Hi Rohit,

Thank you so much for your time and consideration. But let's say I want to extract a specific range of data from my column data points for fitting; how to do that?

Sorry for the silly question. For a beginner, I am struggling to learn. It would be helpful if you answer this.

Regards, Soumyaranjan
POSTED BY: Soumyaranjan Jhankar
Rohit Namjoshi
Rohit Namjoshi
Posted 2 years ago

Hi Soumyaranjan,

This is an empty list, so all of the data is being filtered out, so DataxzStein is empty.

Select[DataxyzStein, -10^-7 <= #[[2]] <= 10^-7 &]

There are four columns in the data which columns are x, y, z? What is the fourth column?
POSTED BY: Rohit Namjoshi

Hi Rohit !! 1st 3 columns are x, y and z, respectively. The 4t one is the Electric Potential which is a function of x, y and z. Since I want to fit in the XZ plane, so I want to drop the y column.

Please help me to fit those data. Thank you for your time and consideration.

POSTED BY: Soumyaranjan Jhankar
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