(octave.info)Terminal Output
14.1.1 Terminal Output
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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.
-- : disp (X)
-- : STR = disp (X)
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: Note: fdisp.
-- : list_in_columns (ARG, WIDTH, PREFIX)
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: Note: terminal_size.
-- : terminal_size ()
Return a two-element row vector containing the current size of the
terminal window in characters (rows and columns).
See also: Note: list_in_columns.
-- : format
-- : format options
-- : [FORMAT, FORMATSPACING] = format
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 =
+.-
-.+
bank
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.
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).
If called with one or two output arguments, and no inputs, return
the current format and format spacing.
See also: Note: fixed_point_format, Note:
output_precision, *note split_long_rows:
XREFsplit_long_rows, *note print_empty_dimensions:
XREFprint_empty_dimensions, Note: rats.
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