Define a variable from an equation

Hi,

I have an equation with x and y are variable and a, b and d are constant.

with x =[1:1:10];

How to define y variable?

[KSSV]

You want to solve for y?

[ly]

I want to know y based on x =[1:1:10];

Example:

x=1, y=???

x=2, y=???

Answer 1

[Walter Roberson]

As I posted in your earlier question,

y1 = @(b, d, x) -b .* (exp(-(2/3) .* lambertw(-3 .* (b.^3 ./ a.^2).^(1/2) .* d.^3 ./ x.^3)) .* d.^2 - x.^2) ./ x.^2
y2 = @(b, d, x) -b .* (exp(-(2/3) .* lambertw(3 .* (b.^3 ./ a.^2).^(1/2) .* d.^3 ./ x.^3)) .* d.^2 - x.^2) ./ x.^2;

Now use y1(b, d, 1:10) and y2(b, d, 1:10)

Note: you will need the Symbolic Toolbox for lambertw, but see also https://www.mathworks.com/matlabcentral/fileexchange/43419-the-lambert-w-function

[ly]

Thanks,

How to get y1, y2 from equation.

[Walter Roberson]

Symbolic toolbox with x symbolic, and solve() . You can then matlabFunction() and pass the numeric x values in .

The y1 and y2 are there because there are two solutions.

[ly]

syms a b d x y

Y=solve( '1/a*(b-y)^1.5-log(b/x)+0.5*log(1-y/b)=0',y);

Y

But Y is [empty sym], I use Matlab R2011b

Answer 2

[KSSV]

doc solve.

[ly]

Yes, but "solve" only get 1 value y from 1 value x.

My case, x is matrix adn I want y is a matrix like x.