GNU Octave: Converting Numerical Data to Strings

Previous: Concatenating Strings, Up: Creating Strings [Contents][Index]

#### 5.3.2 Converting Numerical Data to Strings

Apart from the string concatenation functions (see 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 (see Formatted Output, sprintf).

Function File: s = mat2str (x, n)
Function File: 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: sprintf, num2str, int2str.

Function File: num2str (x)
Function File: num2str (x, precision)
Function File: 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` (see Formatted Output). `num2str` can also handle 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"

  Notes:

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

  The `num2str` function is not very flexible. For better control over the results, use `sprintf` (see Formatted Output).

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

  See also: sprintf, int2str, mat2str.

Function File: 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` (see Formatted Output).

  See also: sprintf, num2str, mat2str.

Previous: Concatenating Strings, Up: Creating Strings [Contents][Index]