5.6 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 non-negative 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 non-negative 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 non-negative 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.

Loadable Function: s = num2hex (n)

Typecast a double precision number or vector to a 16 character hexadecimal string of the IEEE 754 representation of the number. For example

num2hex ([-1, 1, e, Inf, NaN, NA]); ⇒ "bff0000000000000 3ff0000000000000 4005bf0a8b145769 7ff0000000000000 fff8000000000000 7ff00000000007a2"

See also: hex2num, hex2dec, dec2hex.

Loadable Function: n = hex2num (s)

Typecast the 16 character hexadecimal character matrix to an IEEE 754 double precision number. If fewer than 16 characters are given the strings are right padded with '0' characters.

Given a string matrix, hex2num treats each row as a separate number.

hex2num (["4005bf0a8b145769";"4024000000000000"]) ⇒ [2.7183; 10.000]

See also: num2hex, 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

See also: str2num.

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. For example:

strjust (["a"; "ab"; "abc"; "abcd"]) ⇒ ans = a ab abc abcd

Function File: str2num (s)

Convert the string (or character array) s to a number (or an array). Examples:

str2num("3.141596") ⇒ 3.141596 str2num(["1, 2, 3"; "4, 5, 6"]); ⇒ ans = 1 2 3 4 5 6

Caution: As str2num uses the eval function to do the conversion, str2num will execute any code contained in the string s. Use str2double instead if you want to avoid the use of eval.

See also: str2double, eval.

Mapping Function: toascii (s)

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

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

See also: char.

Mapping Function: tolower (s)

Mapping Function: lower (s)

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

tolower ("MiXeD cAsE 123") ⇒ "mixed case 123"

See also: toupper.

Built-in Function: toupper (s)

Built-in Function: upper (s)

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

toupper ("MiXeD cAsE 123") ⇒ "MIXED CASE 123"

See also: tolower.

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.