How to find the unknown (value of 'a', which has more than 1 answers), if we already have known data from excel?

Dear All,

Currently I have alot of data (in excel format from experimental measurement). I need to find an unknown from a equation, where the X and Y value of data to be included in the equation. I have run few codes, but could not find the unknown 'a' as error "Empty sym: 0-by-1" keep pop up once I troed to solve the equation.

Below are the is the:

1) Example of data:

2) Details and equation used:

load Data.txt
syms a % unknown 'a'
d = 700e-6
rad = d./2
t = 1000e-6
c = 345.2
n = 1.83e-5
den = 1.189
X = Data(:,1)% X data from excel
w = 2*pi*X
D = 0.0042
p = 0.00615
k = rad*sqrt((w*den)/n)
Z1 = (((32*n*t)/(d.^2))*(1+(k.^2)/32).^(1/2))
z = Z1/(p*den*c)
Rs = (1/2)*(sqrt(2*n*den*w))
Y = Data(:,2) % Y data from excel
eqns = z + ((2*a*Rs)/(p*den*c)) == Y %Answer of the eqns is equal to Y values
solv = solve (eqns,a)
plot (X,a)

Above is the latest code I have run. Supposedly, my expectation, I will get 5 different values of 'a' and at the end I will plot graph X versus a to proceed to the next step.

Anyone can give and advice why this problem happens, do I have correct my code.

Any help will be appreciated.

Thank you.

Regards,

Nur Arafah

[darova]

why not use

a = (Y-z).*(p.*den.*c)./(2.*Rs);

[Jafar Nur Arafah]

Dear darova,

Thanks for your reply.

I had try it before but it not working. Maybe at that time the code was wrong. Will try again with your suggestion.

Thank you very much.

[Jafar Nur Arafah]

Hi darova,

Finally it works.

Thank you!! =)