Getting error as no solution was found. Try changing the guess value

[vveeran]

Hi all,

I am getting  error as no solution was found. Try changing the guess value TOL or CTOL.

could someone help me.

I attached my code below,

[MikeArmstrong · Accepted solution]

Your formula seems to be returning a complex result.

[vveeran]

Thank you for your answer.

How can I avoid getting the complex result in this formula.

What parameters do I need to change.

[MikeArmstrong]

Have a look and see if the attached helps. I have changed Find for Minerr so the solve block converges. However, your answer changes when the estimate for I is changed. Are you sure your formula and inputs are correct.

Mike

[vveeran]

Thank you  @Mike Armstrong

[MikeArmstrong]

You are welcome. I am sure one of the other users will provide a more detailed comprehensive answer.

Mike

[StuartBruff]

Mike Armstrong wrote:

You are welcome. I am sure one of the other users will provide a more detailed comprehensive answer.

I don't know about "comprehensive", but there's a discontinuity at x1 = 300, after which the exponential goes positive and rises into the numeric stratosphere pretty rapidly.  Hence, you are right to wonder about the validity of the equations if x1 is meant to have values >= 300.  The reason Find won't work is that there doesn't appear to be a real solution that makes the expression equal to zero, and starting from x1 > 300 is going to give the numerical solver kittens.  Solving the expression symbolically for x1 gives a nice equation involving LambertW functions.

Stuart

[MikeArmstrong]

Really nice work Stuart.

[AlvaroDíaz]

Hi Stuart. Also, without found a change of sign, can't be sure if there are a real root. This is the same, but more compact.

[vveeran]

Thank you all for your valuable comments.