The Loc(), Loc Nonmissing(), Loc Min(), Loc Max(), and Loc Sorted() functions all return matrices that show positions of certain values in a matrix.
The Loc() function creates a matrix of positions that locate where A is true (nonzero and nonmissing).
A = [0 1 . 3 4 0];
B = [2 0 0 2 5 6];
The following example returns the indices for the values of A that are nonmissing and nonzero.
I = Loc( A );
[2, 4, 5]
The following example returns the indices for the values of A that are less than the corresponding values of B. Note that the two matrices must have the same number of rows and columns.
I = Loc( A < B );
[1, 5, 6]
The following script replaces all values less than 4 in A with 0.
A = [0 1 0 3 4 0];
A[Loc( A < 4 )] = 0;
Show( A );
A = [0 0 0 0 4 0];
The following script returns an empty matrix:
Loc( [2 3 4 5 6] > 7 );
[](0, 1)
The Loc Nonmissing() function returns a vector of row numbers in a matrix that do not contain any missing values. For example,
A = [1 2 3, 4 . 6, 7 8 ., 8 7 6];
Loc Nonmissing( A );
[1, 4]
The Loc Min() and Loc Max() functions return the position of the first occurrence of the minimum and maximum elements of a matrix. Elements of a matrix are numbered consecutively, starting in the first row, first column, and proceeding left to right.
A = [1 2 2, 2 4 4, 1 1 1];
B = [6, 12, 9];
Show( Loc Max( A ) );
Show( Loc Min( B ) );
Loc Max(A) = 5;
Loc Min(B) = 1;
The Loc Sorted() function is mainly used to identify the interval that a number lies within. The function returns the position of the highest value in A that is less than or equal to the value in B. The resulting vector contains an item for each element in B.
A = [10 20 30 40];
B = [35];
Loc Sorted( A, B );
[3]
A = [10 20 40];
B = [35 5 45 20];
Loc Sorted( A, B );
[2, 1, 3, 2]
Here’s an example that defines a list of strings. Loc Sorted() identifies the string at the seventh interval and puts it in a list.
{"No Fat", "Some Fat", "Low Fat", "Normal Fat", "Medium Fat", "High Fat"}
[Loc Sorted( [0, 1, 5, 10, 20, 25], 7)]
{"Low Fat"}
To convert the returned value to a string, include the subscript [1] at the end of the expression:
{"No Fat", "Some Fat", "Low Fat", "Normal Fat", "Medium Fat", "High Fat"}
[Loc Sorted( [0, 1, 5, 10, 20, 25], 7)][1]
"Low Fat"
Notes:
• A must be sorted in ascending order.
• The returned values are always 1 or greater. If the element in B is smaller than all of the elements in A, then the function returns a value of 1. If the element in B is greater than all of the elements in A, then the function returns n, where n is the number of elements in A.