python - Convert Value History to Plot in Swift 3 -


i have pretty simple coupled bvp system solve , plot. made simple, powerful python code. however, swift doesn't so hell trying integrate swift , gave (if has proven solution such integration, ears). c++ easier integrate has ode solvers in odeint. decided own little algorithm in swift, isn't bad in terms of calculations. problem converting value history plot. after have tried searching, nothing useful seems show up. @ moment, have in playground , part under "// display final solution in history" shows plots when click value histories of x , v there.

i need produce graph python did me.

import uikit typealias solver = (double, double, double) -> void  struct {     var th1 = 0.0     var tc2 = 0.0     var deltat = 0.0      init(th1: double, tc2: double, deltat: double) {         self.th1 = th1         self.tc2 = tc2         self.deltat = deltat     }      func solveusingsolver(solver: solver) {         solver(th1, tc2, deltat)     } }  func solveeuler(th1: double, tc2: double, t : double) {      var x = th1      var = 0.0     var upper = th1     var lower = tc2     var vold = (lower + upper) / 2     var v = vold     var xold = x     let epsilon = 0.05     var err = 1.0      var xarray: [double] = [0,1,2,3,4,5,6,7,8,9,10]     var varray: [double] = [0,1,2,3,4,5,6,7,8,9,10]      var j=0      while (err > epsilon) {         while < 1 {             v -= 4*t*i*(xold-vold)             x -= t*i*(xold-vold)             xold = x             vold = v             i+=t             xarray[j]=x             varray[j]=v             j += 1         }          err = abs(varray[10] - tc2)          if varray[10] > tc2 {             upper = varray[0]             }         else {             lower = varray[0]         }          x = th1         xold = x         vold = (lower + upper) / 2         v = vold         i=0.0         j=0      }      print(xarray)     print(varray)      // display final solution in history     while < 1 {         v -= 4*t*i*(xold-vold)         x -= t*i*(xold-vold)         xold = x         vold = v         i+=t         xarray[j]=x         varray[j]=v         j += 1     }  } let prob = he(th1: 100.0, tc2: 25.0, deltat: 0.1) prob.solveusingsolver(solver:solveeuler)

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if you're curious, it's solving t1 = 100, t2 = 25, h1 = zeta, h2 = 4*zeta

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