ELEMENT   (x, y)   ; 
            
The ELEMENT function returns a matrix that is the same shape as x. The return value indicates which elements of x are elements of y. In particular, if A = element(x, y), then 
         
| ![\[  A_ i = \left\{  \begin{array}{ll} 1 &  \mbox{if}~  x_ i \in y \\ 0 &  \mbox{otherwise} \end{array} \right.  \]](images/imlug_langref0301.png) | 
The arguments are as follows:
specifies a matrix of elements to test for membership.
specifies a set.
If the intersection between x and y is empty, then the ELEMENT function returns a zero matrix. If x is a proper subset of y, then the ELEMENT function returns a matrix of ones. In general, the ELEMENT function returns 1 for elements in the intersection of x and y, as shown in the following statements:
x = {0, 0.5, 1, 1.5, 2, 2.5, 3, 0.5, 1.5, 3, 3, 1};
set = {0 1 3}`;
b = element(x, set);
n = sum(b);        /* number of elements of X that are in SET */
idx = t(loc(b));   /* indices of elements of X that are in SET */
values = x[idx];   /* values of elements of X that are in SET */
print n idx values;
Figure 23.108: Elements That Belong to a Set
| n | idx | values | 
|---|---|---|
| 6 | 1 | 0 | 
| 3 | 1 | |
| 7 | 3 | |
| 10 | 3 | |
| 11 | 3 | |
| 12 | 1 |