Next: Terminal Input, Up: Basic Input and Output [Contents][Index]
Since Octave normally prints the value of an expression as soon as it has been evaluated, the simplest of all I/O functions is a simple expression. For example, the following expression will display the value of ‘pi’
pi -| pi = 3.1416
This works well as long as it is acceptable to have the name of the
variable (or ‘ans’) printed along with the value. To print the
value of a variable without printing its name, use the function
disp
.
The format
command offers some control over the way Octave prints
values with disp
and through the normal echoing mechanism.
Display the value of x.
For example:
disp ("The value of pi is:"), disp (pi) -| the value of pi is: -| 3.1416
Note that the output from disp
always ends with a newline.
If an output value is requested, disp
prints nothing and returns the
formatted output in a string.
See also: fdisp.
Return a string containing the elements of arg listed in columns with an overall maximum width of width and optional prefix prefix.
The argument arg must be a cell array of character strings or a character array.
If width is not specified or is an empty matrix, or less than or equal to zero, the width of the terminal screen is used. Newline characters are used to break the lines in the output string. For example:
list_in_columns ({"abc", "def", "ghijkl", "mnop", "qrs", "tuv"}, 20) ⇒ abc mnop def qrs ghijkl tuv whos ans ⇒ Variables in the current scope: Attr Name Size Bytes Class ==== ==== ==== ===== ===== ans 1x37 37 char Total is 37 elements using 37 bytes
See also: terminal_size.
Return a two-element row vector containing the current size of the terminal window in characters (rows and columns).
See also: list_in_columns.
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 (default).
long
Fixed point format with 16 significant figures.
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. In the long format, double values are displayed with 16
significant digits and single values are displayed with 8. 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 3.141592653589793E+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 31.416e+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 is a raw format equivalent to the C++ code
std::cout << variable
. In general, the result is a presentation
with 6 significant digits where unnecessary precision (such as trailing zeros
for integers) is suppressed. Complex numbers are 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 useful for examining the sparsity structure of a large matrix.
For very large matrices the function spy
which plots the sparsity
pattern will be clearer.
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 "+" "+-."
, the matrix
[1, 0, -1; -1, 0, 1]
is displayed as
ans = +.- -.+
Print variable in a format appropriate for a currency (fixed format with two digits to the right of the decimal point). Only the real part of a variable is displayed, as the imaginary part makes no sense for a currency.
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
.
The same as native-hex
, but always print the most significant byte
first.
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.
The same as native-bit
, but always print the most significant bits
first.
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).
If called with one or two output arguments, and no inputs, return the current format and format spacing.
See also: fixed_point_format, output_precision, split_long_rows, print_empty_dimensions, rats.
• Paging Screen Output: |
Next: Terminal Input, Up: Basic Input and Output [Contents][Index]