Info Catalog octave: Bit Manipulations octave: Numeric Data Types octave: Promotion and Demotion of Data Types

octave: Logical Values

 
 4.6 Logical Values
 ==================
 
 Octave has built-in support for logical values, i.e., variables that are
 either ‘true’ or ‘false’.  When comparing two variables, the result will
 be a logical value whose value depends on whether or not the comparison
 is true.
 
    The basic logical operations are ‘&’, ‘|’, and ‘!’, which correspond
 to “Logical And”, “Logical Or”, and “Logical Negation”.  These
 operations all follow the usual rules of logic.
 
    It is also possible to use logical values as part of standard
 numerical calculations.  In this case ‘true’ is converted to ‘1’, and
 ‘false’ to 0, both represented using double precision floating point
 numbers.  So, the result of ‘true*22 - false/6’ is ‘22’.
 
    Logical values can also be used to index matrices and cell arrays.
 When indexing with a logical array the result will be a vector
 containing the values corresponding to ‘true’ parts of the logical
 array.  The following example illustrates this.
 
      data = [ 1, 2; 3, 4 ];
      idx = (data <= 2);
      data(idx)
           ⇒ ans = [ 1; 2 ]
 
 Instead of creating the ‘idx’ array it is possible to replace
 ‘data(idx)’ with ‘data( data <= 2 )’ in the above code.
 
    Logical values can also be constructed by casting numeric objects to
 logical values, or by using the ‘true’ or ‘false’ functions.
 
  -- : logical (X)
      Convert the numeric object X to logical type.
 
      Any nonzero values will be converted to true (1) while zero values
      will be converted to false (0).  The non-numeric value NaN cannot
      be converted and will produce an error.
 
      Compatibility Note: Octave accepts complex values as input, whereas
      MATLAB issues an error.
 
DONTPRINTYET       See also: double XREFdouble, single XREFsingle, *noteDONTPRINTYET       See also: double XREFdouble, single XREFsingle, 
      char XREFchar.
 
  -- : true (X)
  -- : true (N, M)
  -- : true (N, M, K, ...)
      Return a matrix or N-dimensional array whose elements are all
      logical 1.
 
      If invoked with a single scalar integer argument, return a square
      matrix of the specified size.
 
      If invoked with two or more scalar integer arguments, or a vector
      of integer values, return an array with given dimensions.
 
      See also: false XREFfalse.
 
  -- : false (X)
  -- : false (N, M)
  -- : false (N, M, K, ...)
      Return a matrix or N-dimensional array whose elements are all
      logical 0.
 
      If invoked with a single scalar integer argument, return a square
      matrix of the specified size.
 
      If invoked with two or more scalar integer arguments, or a vector
      of integer values, return an array with given dimensions.
 
      See also: true XREFtrue.
 

Info Catalog octave: Bit Manipulations octave: Numeric Data Types octave: Promotion and Demotion of Data Types