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I'm trying to write Mathematica code to use Kramers-Kronig on a csv file with 2 columns.

  • Column 1 is h(eV). It goes from 0 to 6, in increments of 0.1.
  • Column 2 is alpha (cm^-1).

For some reason, my code just outputs a blank graph. Can someone please tell me what's wrong with it?

This is the equation I'm trying to implement (thanks J.M. for doing the latex) $$n_r(\hbar\omega)-1=\frac{c\cdot h}{2\pi^2}P\int_0^\infty \frac{\alpha(\hbar\omega^\prime)}{(\hbar\omega^\prime)^2-(\hbar\omega)^2}d(\hbar\omega^\prime)$$

The reason I posted on this forum is that my code is based on the code from a topic on Physics SE (Update: wrong link, see comments below)

c = 300000000;
data = Import["kk.csv", "CSV"];
column1 = data[[All, 1]];
column2 = data[[All, 2]];
Delete[column1, 1];
Delete[column2, 1];

output := 
  1 + (c PlanckConstant)/(2 pi^2) 
    NIntegrate[column2/(column1^2 - omega^2), {omega, (column1)^2, 0, infinity}, 
      Method -> "PrincipalValue", Exclusions -> Automatic]

Plot[output, {column1, 0, 6}, AxesOrigin -> {0, 0}]

migration rejected from physics.stackexchange.com Oct 9 at 5:43

This question came from our site for active researchers, academics and students of physics. Votes, comments, and answers are locked due to the question being closed here, but it may be eligible for editing and reopening on the site where it originated.

closed as off-topic by Jens, RunnyKine, Öskå, m_goldberg, Yves Klett Oct 9 at 5:43

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question cannot be answered without additional information. Questions on problems in code must describe the specific problem and include valid code to reproduce it. Any data used for programming examples should be embedded in the question or code to generate the (fake) data must be included." – Jens, RunnyKine, Öskå, m_goldberg, Yves Klett
If this question can be reworded to fit the rules in the help center, please edit the question.

Since you mention in the comments on your Physics post that you took the code from that site instead of this one, did you take a look at the solution on this site? –  rm -rf Apr 15 '13 at 2:06
Without access to your data, it is hard to experiment with your code. However, I wonder if it wouldn't help to use column1 = data[[2 ;; -1, 1]]; column2 = data[[2 ;; -1, 2]]; in place of the last four lines in the first code group. –  m_goldberg Apr 15 '13 at 2:19
@rm -rf: On the Physics post, my last comment had been that I made a mistake, and actually I was in error, therefore the post should be migrated. That comment seems to have been eaten during migration. Actually, I got the code from mathematica.stackexchange.com/questions/1750/… –  o_0 Apr 15 '13 at 2:26
@m_goldberg: Here's a link to the data: 4shared.com/file/YSfGsekq/kk_online.html I will try your commands. If you don't mind me asking, what do they do? –  o_0 Apr 15 '13 at 2:34
OK, I tried the commands. When I used an upper integration limit of 800 instead of infinity, I got errors like "NIntegrate::slwcon: Numerical integration converging too slowly; suspect one of the following: singularity, value of the integration is 0, highly oscillatory integrand, or WorkingPrecision too small." I tried infinity, and I'll let you know what happens when it finishes. –  o_0 Apr 15 '13 at 2:41

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