Message Boards

WOLFRAM COMMUNITY

4187 Views

1 Reply

1 Total Likes

View groups...

Follow this post

Share this post:

GROUPS:

Fit the data with Bessel functions using FindFit?

Qiang Li

Qiang Li, SUSTech

Posted 5 years ago

Consider the following code: fp = {{1.9, 27.9}, {3.42, 42.8}, {4.94, 53.2}, {6.46, 56.8}, {7.98, 60.3}, {9.5, 61.4}, {11.02, 63.1}, {12.54, 66}}; FindFit[fp, {1/ 1000\[Sqrt](R3.0810^19(0.04510^101.4810^3(310^8)^2( R3.0810^19)/( 2(1.93.0810^19)^3)(BesselI[0, (R3.0810^19)/( 21.93.0810^19)] BesselK[0, (R3.0810^19)/(21.93.0810^19)] - BesselI[1, (R3.0810^19)/(21.93.0810^19)]* BesselK[1, (R3.0810^19)/(21.93.0810^19)]) + 0.04510^10b(310^8)^2(R3.0810^19)/(21.93.0810^19) BesselI[1, (R3.0810^19)/(21.93.0810^19)] BesselK[1, ( R3.0810^19)/(21.93.0810^19)]) + c/2(310^8)^2R3.0810^19 - 1.110^-52(310^8)^2(R3.08*10^19)^2), {10^-40 <= b <= 10^-37, 10^-29 <= c <= 10^-26}}, {b, c}, R] mathematica gives me a obvious wrong result, I don't know, maybe FindFit can't fit for Bessel function?

Consider the following code:

fp = {{1.9, 27.9}, {3.42, 42.8}, {4.94, 53.2}, {6.46, 56.8}, {7.98, 
    60.3}, {9.5, 61.4}, {11.02, 63.1}, {12.54, 66}};
FindFit[fp, {1/
   1000*\[Sqrt](R*3.08*10^19*(0.045*10^10*1.48*10^3*(3*10^8)^2*(
          R*3.08*10^19)/(
          2*(1.9*3.08*10^19)^3)*(BesselI[0, (R*3.08*10^19)/(
              2*1.9*3.08*10^19)]*
             BesselK[0, (R*3.08*10^19)/(2*1.9*3.08*10^19)] - 
            BesselI[1, (R*3.08*10^19)/(2*1.9*3.08*10^19)]*
             BesselK[1, (R*3.08*10^19)/(2*1.9*3.08*10^19)]) + 
         0.045*10^10*b*(3*10^8)^2*(R*3.08*10^19)/(2*1.9*3.08*10^19)*
          BesselI[1, (R*3.08*10^19)/(2*1.9*3.08*10^19)] BesselK[1, (
           R*3.08*10^19)/(2*1.9*3.08*10^19)]) + 
      c/2*(3*10^8)^2*R*3.08*10^19 - 
      1.1*10^-52*(3*10^8)^2*(R*3.08*10^19)^2), {10^-40 <= b <= 10^-37,
    10^-29 <= c <= 10^-26}}, {b, c}, R]

mathematica gives me a obvious wrong result, I don't know, maybe FindFit can't fit for Bessel function?

POSTED BY: Qiang Li

1 Reply

Sort By:

Moderation Team

Moderation Team, WOLFRAM

Posted 5 years ago

Welcome to Wolfram Community! Please make sure you know the rules: https://wolfr.am/READ-1ST Please post detailed clear questions. The rules explain how to format your code properly. If you do not format code, it may become corrupted and useless to other members. Please EDIT your post and make sure code blocks start on a new paragraph and look framed and colored like this. int = Integrate[1/(x^3 - 1), x]; Map[Framed, int, Infinity]

POSTED BY: Moderation Team

Reply to this discussion

Reply Preview

Attachments

Remove Add a file to this post

Follow this discussion

or Discard

Group Abstract

Feedback