Why do I get NAN?

383 views (last 30 days)
Yasmin Tamimi
Yasmin Tamimi on 19 Jan 2014
Hey everyone,
I'm running this equation
hMphi(1) = - (dd_Anis(1) * ddu_acos(1) * du_dMphi(1))/(C2*sin(Mtheta(1)))- ((Is*P_hbar/(2*P_Q*g*C2))*((ephix(1)*Ffx(1))+(ephiy(1)*Ffy(1))))- Ms*(Ny-Nx)*sin(Mtheta(1))*sin(2*Mphi(1))+ (Happy*cos(Mphi(1)) - Happx*sin(Mphi(1))) ;
in a loop and a certain point the value of this vector becomes a NAN?! Can Anyone tell me why is this happening? I' dividing by a sin, so I thought that maybe the problem is from it, but I printed the values of it I didn't get Inf.
Thanks

Accepted Answer

Roger Stafford
Roger Stafford on 19 Jan 2014
Any of these arithmetic operations will produce a NaN: zero/zero, zero*infinity, infinity/infinity, infinity-infinity. For example, if any of the three quantities, dd_Anis, ddu_acos, or du_dMph were to become zero at the same time that sin(Mtheta) is zero, that would produce a NaN. You should make a test on hMphi each time it is computed and arrange to stop if a NaN is detected so you can check all the values that go into your equation at that point.

More Answers (2)

Jan
Jan on 19 Jan 2014
You can stop the code automatically, when the NaN appears:
dbstop if naninf
Then inspect the local variables and evaluate the different parts of the equation in the command window until you find the reason for the NaN.
  1 Comment
Dheeraja Karthikeyan
Dheeraja Karthikeyan on 25 Apr 2020
Thanks a lot for this! You were a blessing in disguise!

Sign in to comment.


Anna
Anna on 19 Jan 2014
Have you tried to isolate the part of the equation where the fault is at? Debug the equation in the loop iteration before the equation turns into a NaN.

Categories

Find more on Loops and Conditional Statements in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!