bvp4c/bvp5c error

Dear MathWorks Community,

I am trying to use bvp4c/bvp5c and I always get the error:

"Error using char/eps

Too many input arguments.

Error in decomposition/isIllConditioned (line 600)

isIllCond = rc < eps('like',rc) || isnan(rc);

Error in bvp4c (line 196)

if isIllConditioned(dPHIdy)

Error in bratubvp (line 10)

sol1 = bvp4c(@bratuode,@bratubc,solinit,options);"

The code that I am trying to run is the bratubvp.m that is taken from:

https://www.mathworks.com/matlabcentral/fileexchange/3819-tutorial-on-solving-bvps-with-bvp4c

Any example that I am trying to run I always get the same error above. I am wondering whether someone else has run into a same issue and whether this can be resolved or not.

Thank you in advance for your help!

Answer 1

[Torsten]

Did you create a function with name "eps" ? Then you should rename it because "eps" is an internal MATLAB function.

[Efstathios Charalampidis]

Dear Torsten,

Thank you for your reply and help.

Looking at this function, it appears that I have not created any function with name "eps". A quick look in MATLAB shows that:

>> which eps

built-in (/home/stathis/Documents/MATLAB/R2022b/toolbox/matlab/elmat/eps)

Do you have any other suggestions?

Many thanks in advance for your help.

All the best,

Stathis.

[Torsten]

Do you have the same problems with this test code ?

If yes: what is the exact error message ?

xmesh = linspace(0,pi/2,5);
solinit = bvpinit(xmesh, @guess);
sol = bvp4c(@bvpfcn, @bcfcn, solinit);
plot(sol.x, sol.y, '-o')

function dydx = bvpfcn(x,y)
  dydx = [y(2);-y(1)];
end

function res = bcfcn(ya,yb)
  res = [ya(1);yb(1)-2];
end

function g = guess(x)
  g = [sin(x);cos(x)];
end

[Efstathios Charalampidis]

Dear Torsten,

The error is the same as before:

Error using char/eps

Too many input arguments.

Error in decomposition/isIllConditioned (line 600)

isIllCond = rc < eps('like',rc) ||

isnan(rc);

Error in bvp4c (line 196)

if isIllConditioned(dPHIdy)

Error in untitled (line 3)

sol = bvp4c(@bvpfcn, @bcfcn, solinit);

[Torsten]

What is the output of

which -all eps

?

What is

char/eps

?

[Efstathios Charalampidis]

Dear Torsten,

I was able to locate the error. I have installed the advanpix package (for multi-precision computing), and the flag "-all" gave me a hint about it. Thanks a lot!