is is used to check properties of sdpvar and constraint objects.

```
yesno = is(x,'property')
```

Checking if an sdpvar object is linear can be done as follows.

```
x = sdpvar(1,1);
y = [x;x*x];
is(y,'linear')
ans =
0
```

The command works almost in the same way on constraints, with the difference that the check is performed on every constraint in the set object separately, so the output can be a vector

```
x = sdpvar(1,1);
F = [x>=1, [1 x;x 1]>=0, x<=3];
is(F,'elementwise')
ans =
1
0
1
```

Hence, creating a set object containing only the element-wise constraints is done with

```
F_element = F(is(F,'elementwise'));
```

There are numerous conditions that can be checked both for sdpvar objects

```
x = sdpvar(1,1);
is(x,'real')
is(x,'complex')
is(x,'linear')
is(x,'bilinear')
is(x,'quadratic')
is(x,'nonlinear')
is(x,'sigmonial')
is(x,'homogeneous')
is(x,'symmetric')
is(x,'hermitian')
is(x,'scalar')
is(x,'integer')
is(x,'binary')
```

and constraints

```
x = sdpvar(1,1);
F = set(x > 0);
is(x,'equality')
is(F,'elementwise')
is(x,'socc')
is(x,'sdp')
is(x,'sos')
is(x,'linear')
is(x,'lmi')
```