Changing parameter in a function when called by bvp4c

I have a system of ode's I want to solve using bvp4c, which depend on a (known) parameter, e.g

function dydx = bvpeq(x,y)
  k = 2;
  dydx(1) = y(2) + k*x
  dydx(2) = y(1) + k*x
end

Plus a guess bvpguess and boundry conditions bvpbc which don't depend on k. Then I want to vary k and have an array which contains the first few points of the solution for each k.

xmesh= linspace(1,5);
solinit = bvpinit(xmesh, @bvpguess);
sol = bvp4c(@bvpeq, @bvpbc, solinit);
y1vals(1,1:10) = sol.y(1,1:10);
y2vals(1,1:10) = sol.y(2,1:10);
xvals(1,1:10) = sol.x(1:10);

I then vary k by manually chaning the value of k and the rows of y1vals, y2vals, and xvals that I'm inputting in, but I want to do this with a for loop

for j = 1:10
  xmesh= linspace(1,5);
  solinit = bvpinit(xmesh, @bvpguess);
  sol = bvp4c(@bvpeq, @bvpbc, solinit);
  y1vals(j,1:10) = sol.y(1,1:10);
  y2vals(j,1:10) = sol.y(2,1:10);
  xvals(j,1:10) = sol.x(1:10);
end

function dydx = bvpeq(x,y)
  k = j;
  dydx(1) = y(2) + k*x
  dydx(2) = y(1) + k*x
end

But j is an unrecognised variable in the function, is there a way I can change the value of k in bvpeq, or generate 10 functions (bvpeq1, bvpeq2, etc) with different values of k?

Answer 1

[Star Strider]

If you want to pass ‘k’ as an extra parameter, see the documentation section on Passing Extra Parameters for relevant examples.

So:

function dydx = bvpeq(x,y,k)
  dydx(1) = y(2) + k*x
  dydx(2) = y(1) + k*x
end

and:

sol = bvp4c(@(x,y)bvpeq(x,y,k), bvpbc, solinit);

I have not tested that here, however it should work (with ‘k’ defined before the bvp4c call).

.

[Lewis]

Thank you, it did work with k definied before the bvp4c call.

[Star Strider]

As always, my pleasure!

.