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Operators and Keywords

Function List:

C++ API

: format
: format options

Reset or specify the format of the output produced by disp and Octave’s normal echoing mechanism.

This command only affects the display of numbers but not how they are stored or computed. To change the internal representation from the default double use one of the conversion functions such as single, uint8, int64, etc.

By default, Octave displays 5 significant digits in a human readable form (option ‘short’ paired with ‘loose’ format for matrices). If format is invoked without any options, this default format is restored.

Valid formats for floating point numbers are listed in the following table.

short

Fixed point format with 5 significant figures in a field that is a maximum of 10 characters wide. (default).

If Octave is unable to format a matrix so that columns line up on the decimal point and all numbers fit within the maximum field width then it switches to an exponential ‘e’ format.

long

Fixed point format with 15 significant figures in a field that is a maximum of 20 characters wide.

As with the ‘short’ format, Octave will switch to an exponential ‘e’ format if it is unable to format a matrix properly using the current format.

short e
long e

Exponential format. The number to be represented is split between a mantissa and an exponent (power of 10). The mantissa has 5 significant digits in the short format and 15 digits in the long format. For example, with the ‘short e’ format, pi is displayed as 3.1416e+00.

short E
long E

Identical to ‘short e’ or ‘long e’ but displays an uppercase ‘E’ to indicate the exponent. For example, with the ‘long E’ format, pi is displayed as 3.14159265358979E+00.

short g
long g

Optimally choose between fixed point and exponential format based on the magnitude of the number. For example, with the ‘short g’ format, pi .^ [2; 4; 8; 16; 32] is displayed as 

ans =

     9.8696
     97.409
     9488.5
 9.0032e+07
 8.1058e+15
short eng
long eng

Identical to ‘short e’ or ‘long e’ but displays the value using an engineering format, where the exponent is divisible by 3. For example, with the ‘short eng’ format, 10 * pi is displayed as 31.4159e+00.

long G
short G

Identical to ‘short g’ or ‘long g’ but displays an uppercase ‘E’ to indicate the exponent.

free
none

Print output in free format, without trying to line up columns of matrices on the decimal point. This also causes complex numbers to be formatted as numeric pairs like this ‘(0.60419, 0.60709)’ instead of like this ‘0.60419 + 0.60709i’.

The following formats affect all numeric output (floating point and integer types).

"+"
"+" chars
plus
plus chars

Print a ‘+’ symbol for matrix elements greater than zero, a ‘-’ symbol for elements less than zero and a space for zero matrix elements. This format can be very useful for examining the structure of a large sparse matrix.

The optional argument chars specifies a list of 3 characters to use for printing values greater than zero, less than zero and equal to zero. For example, with the ‘"+" "+-."’ format, [1, 0, -1; -1, 0, 1] is displayed as 

ans =

+.-
-.+
bank

Print in a fixed format with two digits to the right of the decimal point.

native-hex

Print the hexadecimal representation of numbers as they are stored in memory. For example, on a workstation which stores 8 byte real values in IEEE format with the least significant byte first, the value of pi when printed in native-hex format is 400921fb54442d18.

hex

The same as native-hex, but always print the most significant byte first.

native-bit

Print the bit representation of numbers as stored in memory. For example, the value of pi is 

01000000000010010010000111111011
01010100010001000010110100011000

(shown here in two 32 bit sections for typesetting purposes) when printed in native-bit format on a workstation which stores 8 byte real values in IEEE format with the least significant byte first.

bit

The same as native-bit, but always print the most significant bits first.

rat

Print a rational approximation, i.e., values are approximated as the ratio of small integers. For example, with the ‘rat’ format, pi is displayed as 355/113.

The following two options affect the display of all matrices.

compact

Remove blank lines around column number labels and between matrices producing more compact output with more data per page.

loose

Insert blank lines above and below column number labels and between matrices to produce a more readable output with less data per page. (default).

See also: fixed_point_format, output_max_field_width, output_precision, split_long_rows, print_empty_dimensions, rats.

Package: octave