what is the syntaxis for numerical solvers?

Hi, for the last hour I am trying to start the numerical solver..

The copy-past from "help"

numeric::solve([sin(x) = y^2 - 1, cos(x) = y], [x, y]);

gives

Error: Unexpected MATLAB operator

for '::'

I can also use the other syntaxis option, which works fine in my script:

syms ha r2 positive; [h,rcone] = solve( hh(ha,r2) == 0, VV(ha,r2) == V0);

If use this, how do I define the range of ha and r2 in which I want the solutions?

Answer 1

[Petr]

thanks! but.. how to introduce the range in which I look for solutions? say, x=1..3 ? what's the syntax?

[Walter Roberson]

syms x y
feval(symengine, 'numeric::solve', [sin(x) = y^2 - 1, cos(x) = y], [sym('x=1..3'), y])

[Petr]

! I found the way: using assumptions

Thanks

[Walter Roberson]

Note this from the numeric::solve documentation page:

Note:   In contrast to the symbolic solver solve, the numerical solver does not react to properties of identifiers set via assume. To use these properties, call float ( hold( solve )(arguments)) instead.

Answer 2

[Azzi Abdelmalek]

sol=solve('sin(x) = y^2 - 1', 'cos(x) = y')

%or

sol=solve('sin(x) -y^2 + 1', 'cos(x) - y')

[Chibuzo Chukwu]

How do I make x the subject of this equation.using matlab

x = exp(x+y)

[Walter Roberson]

In older versions of MATLAB,

solve('x = exp(x+y)', 'x')

In more modern versions

syms x y
solve(x == exp(x+y), x)

However, MATLAB is not able to find a solution. A solution exists, and is

-lambertw(-exp(y))

but MATLAB is not strong on Lambert W processing.

Answer 3

[Zuhaib]

it depend on your equation .. write function used in your equation for search in hepl of matlab

Answer 4

[Walter Roberson]

numeric::solve is a MuPAD call that cannot be directly used from MATLAB. Use

feval(symengine, 'numeric::solve', [sym('sin(x) = y^2 - 1'), sym('cos(x) = y')], [sym('x'), sym('y')])

If you have R2011b or later (I think it is), you can use

syms x y
feval(symengine, 'numeric::solve', [sin(x) = y^2 - 1, cos(x) = y], [x, y])

[Petr]

>> syms x y

>> feval(symengine, 'numeric::solve', [sin(x) = y^2 - 1, cos(x) = y], [x, y])

it tells

"Error: The expression to the left of the equals sign is not a valid target for an assignment." to the '=' sign after sin(x).

I tried == instead and it does not work.. Am I doing something completely wrong? Looks like all the toolboxes are installed and it is R2012a

The answer to

>> feval(symengine, 'numeric::solve', [sym('sin(x) = y^2 - 1'), sym('cos(x) = y')], [sym('x'), sym('y')])

is [ empty sym ]

Answer 5

[Chibuzo Chukwu]

How do I make x the subject of this equation.using matlab

x = exp(x+y)