depends

depends returns the internal indicies to all linear variables used in an sdpvar expression or constraint object.

Syntax

k = depends(x)

Examples

sdpvar variables are built-up from internal variable indicies (i.e., the only internal name and reference is an integer).

yalmip('clear')
x = sdpvar(1);
getvariables(x)

ans = 
    1

y = sdpvar(2,3);
getvariables(y)
ans = 
    2 3 4 5 6 7 

For linear expressions, exactly the same result is returned with depends.

depends(x)

ans = 
    1

depends(y)
ans = 
    2 3 4 5 6 7 

For nonlinear expressions the two commands differ. While getvariables returns the internal index to the nonlinear term, depends returns the index to involved linear variables.

z = x^2;
getvariables(z)
ans = 
    8
    
depends(z)    
ans = 
    1

z = x + 3*x^2+y^2;
getvariables(z)
ans = 
    1 8 9
    
depends(z)
ans = 
    1 2