(octave.info)Converting Numerical Data to Strings

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5.3.2 Converting Numerical Data to Strings
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Apart from the string concatenation functions (Note: Concatenating
Strings) which cast numerical data to the corresponding ASCII
characters, there are several functions that format numerical data as
strings.  ‘mat2str’ and ‘num2str’ convert real or complex matrices,
while ‘int2str’ converts integer matrices.  ‘int2str’ takes the real
part of complex values and round fractional values to integer.  A more
flexible way to format numerical data as strings is the ‘sprintf’
function (Note: Formatted Output, Note: sprintf.).

 -- : S = mat2str (X, N)
 -- : S = mat2str (X, N, "class")
     Format real, complex, and logical matrices as strings.

     The returned string may be used to reconstruct the original matrix
     by using the ‘eval’ function.

     The precision of the values is given by N.  If N is a scalar then
     both real and imaginary parts of the matrix are printed to the same
     precision.  Otherwise ‘N(1)’ defines the precision of the real part
     and ‘N(2)’ defines the precision of the imaginary part.  The
     default for N is 15.

     If the argument "class" is given then the class of X is included in
     the string in such a way that ‘eval’ will result in the
     construction of a matrix of the same class.

          mat2str ([ -1/3 + i/7; 1/3 - i/7 ], [4 2])
               ⇒ "[-0.3333+0.14i;0.3333-0.14i]"

          mat2str ([ -1/3 +i/7; 1/3 -i/7 ], [4 2])
               ⇒ "[-0.3333+0i 0+0.14i;0.3333+0i -0-0.14i]"

          mat2str (int16 ([1 -1]), "class")
               ⇒ "int16([1 -1])"

          mat2str (logical (eye (2)))
               ⇒ "[true false;false true]"

          isequal (x, eval (mat2str (x)))
               ⇒ 1

     See also: Note: sprintf, Note: num2str,
     Note: int2str.

 -- : num2str (X)
 -- : num2str (X, PRECISION)
 -- : num2str (X, FORMAT)
     Convert a number (or array) to a string (or a character array).

     The optional second argument may either give the number of
     significant digits (PRECISION) to be used in the output or a format
     template string (FORMAT) as in ‘sprintf’ (Note: Formatted
     Output).  ‘num2str’ can also process complex numbers.

     Examples:

          num2str (123.456)
               ⇒ "123.46"

          num2str (123.456, 4)
               ⇒ "123.5"

          s = num2str ([1, 1.34; 3, 3.56], "%5.1f")
               ⇒ s =
                  1.0  1.3
                  3.0  3.6
          whos s
               ⇒
                Attr Name        Size                     Bytes  Class
                ==== ====        ====                     =====  =====
                     s           2x8                         16  char

          num2str (1.234 + 27.3i)
               ⇒ "1.234+27.3i"

     The ‘num2str’ function is not very flexible.  For better control
     over the results, use ‘sprintf’ (Note: Formatted Output).

     Programming Notes:

     For MATLAB compatibility, leading spaces are stripped before
     returning the string.

     Integers larger than ‘flintmax’ may not be displayed correctly.

     For complex X, the format string may only contain one output
     conversion specification and nothing else.  Otherwise, results will
     be unpredictable.

     Any optional FORMAT specified by the programmer is used without
     modification.  This is in contrast to MATLAB which tampers with the
     FORMAT based on internal heuristics.

     See also: Note: sprintf, Note: int2str,
     Note: mat2str.

 -- : int2str (N)
     Convert an integer (or array of integers) to a string (or a
     character array).

          int2str (123)
               ⇒ "123"

          s = int2str ([1, 2, 3; 4, 5, 6])
               ⇒ s =
                  1  2  3
                  4  5  6

          whos s
               ⇒
                Attr Name        Size                     Bytes  Class
                ==== ====        ====                     =====  =====
                     s           2x7                         14  char

     This function is not very flexible.  For better control over the
     results, use ‘sprintf’ (Note: Formatted Output).

     Programming Notes:

     Non-integers are rounded to integers before display.  Only the real
     part of complex numbers is displayed.

     See also: Note: sprintf, Note: num2str,
     Note: mat2str.