Getting Started

The find Function

The find function determines the indices of array elements that meet a given logical condition. In its simplest form, find returns a column vector of indices. Transpose that vector to obtain a row vector of indices. For example, start again with Dürer's magic square. (See The magic Function.)

• k = find(isprime(A))'
  

picks out the locations, using one-dimensional indexing, of the primes in the magic square:

• k =
       2     5     9    10    11    13
  

Display those primes, as a row vector in the order determined by k, with

• A(k)
  
  ans =
       5     3     2    11     7    13
  

When you use k as a left-hand-side index in an assignment statement, the matrix structure is preserved:

• A(k) = NaN
  
  A =
      16   NaN   NaN   NaN
     NaN    10   NaN     8
       9     6   NaN    12
       4    15    14     1
  

Logical Subscripting

Controlling Command Window Input and Output

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