boussinesq_splineV2.m

function sigma_z=boussinesq_splineV2(q,a,b,z)
  % function that determines stress under corner of an a by b rectangular platform
  % z-meters below the platform. The calculated solutions are in the fmn data
  % m=fmn(:,1)
  % in column 2, fmn(:,2), n=1.2
  % in column 3, fmn(:,2), n=1.4
  % in column 4, fmn(:,2), n=1.6

  fmn= [0.1,0.02926,0.03007,0.03058   %provided data
        0.2,0.05733,0.05894,0.05994
        0.3,0.08323,0.08561,0.08709
        0.4,0.10631,0.10941,0.11135
        0.5,0.12626,0.13003,0.13241
        0.6,0.14309,0.14749,0.15027
        0.7,0.15703,0.16199,0.16515
        0.8,0.16843,0.17389,0.17739];

  m=a/z;  %backslash operator to solve m
  n=b/z;    %backslash for n
  
  m1 = ppval(spline(fmn(:,1),fmn(:,2)),m);  % int. wrt to column 2
  m2 = ppval(spline(fmn(:,1),fmn(:,3)),m);  % int. wrt to column 3
  m3 = ppval(spline(fmn(:,1),fmn(:,4)),m);  % interpolate wrt column 4
  sigma_z = q*ppval(spline([1.2;1.4;1.6],[m1;m2;m3]),n); %interpolates across all previous interpolations
  
end