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5.4 String Conversions

Octave supports various kinds of conversions between strings and numbers. As an example, it is possible to convert a string containing a hexadecimal number to a floating point number.

hex2dec ("FF")
     => ans = 255

Function File: bin2dec (s)

Return the decimal number corresponding to the binary number stored in the string s. For example,

bin2dec ("1110")
=> 14

If s is a string matrix, returns a column vector of converted numbers, one per row of s. Invalid rows evaluate to NaN.

See also dec2hex, base2dec, dec2base, hex2dec, dec2bin

Function File: dec2bin (n, len)

Return a binary number corresponding to the nonnegative decimal number n, as a string of ones and zeros. For example,

dec2bin (14)
=> "1110"

If n is a vector, returns a string matrix, one row per value, padded with leading zeros to the width of the largest value.

The optional second argument, len, specifies the minimum number of digits in the result.

See also bin2dec, dec2base, base2dec, hex2dec, dec2hex

Function File: dec2hex (n, len)

Return the hexadecimal string corresponding to the nonnegative integer n. For example,

dec2hex (2748)
=> "ABC"

If n is a vector, returns a string matrix, one row per value, padded with leading zeros to the width of the largest value.

The optional second argument, len, specifies the minimum number of digits in the result.

See also hex2dec, dec2base, base2dec, bin2dec, dec2bin

Function File: hex2dec (s)

Return the integer corresponding to the hexadecimal number stored in the string s. For example,

hex2dec ("12B")
=> 299
hex2dec ("12b")
=> 299

If s is a string matrix, returns a column vector of converted numbers, one per row of s. Invalid rows evaluate to NaN.

See also dec2hex, base2dec, dec2base, bin2dec, dec2bin

Function File: dec2base (n, b, len)

Return a string of symbols in base b corresponding to the nonnegative integer n.

dec2base (123, 3)
=> "11120"

If n is a vector, return a string matrix with one row per value, padded with leading zeros to the width of the largest value.

If b is a string then the characters of b are used as the symbols for the digits of n. Space (' ') may not be used as a symbol.

dec2base (123, "aei")
=> "eeeia"

The optional third argument, len, specifies the minimum number of digits in the result.

See also base2dec, dec2bin, bin2dec, hex2dec, dec2hex

Function File: base2dec (s, b)

Convert s from a string of digits of base b into an integer.

base2dec ("11120", 3)
=> 123

If s is a matrix, returns a column vector with one value per row of s. If a row contains invalid symbols then the corresponding value will be NaN. Rows are right-justified before converting so that trailing spaces are ignored.

If b is a string, the characters of b are used as the symbols for the digits of s. Space (' ') may not be used as a symbol.

base2dec ("yyyzx", "xyz")
=> 123

See also dec2base, dec2bin, bin2dec, hex2dec, dec2hex

Function File: [num, status, strarray] = str2double (str, cdelim, rdelim, ddelim)

Convert strings into numeric values.

str2double can replace str2num, but avoids the use of eval on unknown data.

str can be the form ‘[+-]d[.]dd[[eE][+-]ddd]’ in which ‘d’ can be any of digit from 0 to 9, and ‘[]’ indicate optional elements.

num is the corresponding numeric value. If the conversion fails, status is -1 and num is NaN.

status is 0 if the conversion was successful and -1 otherwise.

strarray is a cell array of strings.

Elements which are not defined or not valid return NaN and the status becomes -1.

If str is a character array or a cell array of strings, then num and status return matrices of appropriate size.

str can also contain multiple elements separated by row and column delimiters (cdelim and rdelim).

The parameters cdelim, rdelim, and ddelim are optional column, row, and decimal delimiters.

The default row-delimiters are newline, carriage return and semicolon (ASCII 10, 13 and 59). The default column-delimiters are tab, space and comma (ASCII 9, 32, and 44). The default decimal delimiter is ‘.’ (ASCII 46).

cdelim, rdelim, and ddelim must contain only nul, newline, carriage return, semicolon, colon, slash, tab, space, comma, or ‘()[]{}’ (ASCII 0, 9, 10, 11, 12, 13, 14, 32, 33, 34, 40, 41, 44, 47, 58, 59, 91, 93, 123, 124, 125).

Examples:

str2double ("-.1e-5")
=> -1.0000e-006

str2double (".314e1, 44.44e-1, .7; -1e+1")
=>
   3.1400    4.4440    0.7000
 -10.0000       NaN       NaN

line = "200, 300, NaN, -inf, yes, no, 999, maybe, NaN";
[x, status] = str2double (line)
=> x =
    200   300   NaN  -Inf   NaN   NaN   999   NaN   NaN
=> status =
      0     0     0     0    -1    -1     0    -1     0

Function File: strjust (s, ["left"|"right"|"center"])

Shift the non-blank text of s to the left, right or center of the string. If s is a string array, justify each string in the array. Null characters are replaced by blanks. If no justification is specified, then all rows are right-justified.

Function File: str2num (s)

Convert the string s to a number.

Mapping Function: toascii (s)

Return ASCII representation of s in a matrix. For example,

toascii ("ASCII")
     => [ 65, 83, 67, 73, 73 ]

Mapping Function: tolower (s)

Return a copy of the string s, with each upper-case character replaced by the corresponding lower-case one; nonalphabetic characters are left unchanged. For example,

tolower ("MiXeD cAsE 123")
     => "mixed case 123"

Built-in Function: toupper (s)

Return a copy of the string s, with each lower-case character replaced by the corresponding upper-case one; nonalphabetic characters are left unchanged. For example,

toupper ("MiXeD cAsE 123")
     => "MIXED CASE 123"

Built-in Function: do_string_escapes (string)

Convert special characters in string to their escaped forms.

Built-in Function: undo_string_escapes (s)

Converts special characters in strings back to their escaped forms. For example, the expression

bell = "\a";

assigns the value of the alert character (control-g, ASCII code 7) to the string variable bell. If this string is printed, the system will ring the terminal bell (if it is possible). This is normally the desired outcome. However, sometimes it is useful to be able to print the original representation of the string, with the special characters replaced by their escape sequences. For example,

octave:13> undo_string_escapes (bell)
ans = \a

replaces the unprintable alert character with its printable representation.