# depends

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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