Plotting current density using Maxwell's-Ampere law

Hey

Using the magnetic field, I am attempting to plot the current density at the cathode surface. Please find attached a text file. Maxwells-Amperes law has been used to plot it, however the results are not as anticipated. Any suggestion is appreciated.

clc
clear all 
Data=readtable("abs.txt");
Data=Data{:,:};   
Data=Data(~any(isnan(Data),2),:);

t= linspace(0 , 28,15); % creates linearly spaced vectors with increament of 0.2
t = repelem(t,25);
t(end)=[];

Hx=Data(:,4);
Hy=Data(:,5);
Hz=Data(:,6);
x=Data(:,1);
y=Data(:,2);
H=diff(Hx)/0.01-diff(Hy)/0.01;
H=H/1.25663706*10e-6;
H=abs(H);
plot(t,H,'-','LineWidth',2,'LineStyle',':')
xlim([0 30])
ylim([50 600])

[the cyclist]

Can you explain more about the plot you expect to get, and what you think is wrong about this one?