Timing Utilities (GNU Octave)

36.1 Timing Utilities

Octave’s core set of functions for manipulating time values are patterned after the corresponding functions from the standard C library. Several of these functions use a data structure for time that includes the following elements:

usec: Microseconds after the second (0-999999).
sec: Seconds after the minute (0-60). This number can be 60 to account for leap seconds.
min: Minutes after the hour (0-59).
hour: Hours since midnight (0-23).
mday: Day of the month (1-31).
mon: Months since January (0-11).
year: Years since 1900.
wday: Days since Sunday (0-6).
yday: Days since January 1 (0-365).
isdst: Daylight Savings Time flag.
gmtoff: Seconds offset from UTC.
zone: Time zone.

In the descriptions of the following functions, this structure is referred to as a tm_struct.

: seconds = time ()

Return the current time as the number of seconds since the epoch.

The epoch is referenced to 00:00:00 CUT (Coordinated Universal Time) 1 Jan 1970. For example, on Monday February 17, 1997 at 07:15:06 CUT, the value returned by time was 856163706.

See also: strftime, strptime, localtime, gmtime, mktime, now, date, clock, datenum, datestr, datevec, calendar, weekday.

: t = now ()

Return the current local date/time as a serial day number (see datenum).

The integral part, floor (now) corresponds to the number of days between today and Jan 1, 0000.

The fractional part, rem (now, 1) corresponds to the current time.

See also: clock, date, datenum.

: ctime (t)

Convert a value returned from time (or any other non-negative integer), to the local time and return a string of the same form as asctime.

The function ctime (time) is equivalent to asctime (localtime (time)). For example:

ctime (time ())
   ⇒ "Mon Feb 17 01:15:06 1997\n"

See also: asctime, time, localtime.

: tm_struct = gmtime (t)

Given a value returned from time, or any non-negative integer, return a time structure corresponding to CUT (Coordinated Universal Time).

For example:

gmtime (time ())
     ⇒ {
           usec = 0
           sec = 6
           min = 15
           hour = 7
           mday = 17
           mon = 1
           year = 97
           wday = 1
           yday = 47
           isdst = 0
           gmtoff = 0
           zone = GMT
        }

See also: strftime, strptime, localtime, mktime, time, now, date, clock, datenum, datestr, datevec, calendar, weekday.

: tm_struct = localtime (t)

Given a value returned from time, or any non-negative integer, return a time structure corresponding to the local time zone.

localtime (time ())
     ⇒ {
           usec = 0
           sec = 6
           min = 15
           hour = 1
           mday = 17
           mon = 1
           year = 97
           wday = 1
           yday = 47
           isdst = 0
           gmtoff = -21600
           zone = CST
        }

See also: strftime, strptime, gmtime, mktime, time, now, date, clock, datenum, datestr, datevec, calendar, weekday.

: seconds = mktime (tm_struct)

Convert a time structure corresponding to the local time to the number of seconds since the epoch.

For example:

mktime (localtime (time ()))
     ⇒ 856163706

See also: strftime, strptime, localtime, gmtime, time, now, date, clock, datenum, datestr, datevec, calendar, weekday.

: asctime (tm_struct)

Convert a time structure to a string using the following format: "ddd mmm mm HH:MM:SS yyyy\n".

For example:

asctime (localtime (time ()))
     ⇒ "Mon Feb 17 01:15:06 1997\n"

This is equivalent to ctime (time ()).

See also: ctime, localtime, time.

: strftime (fmt, tm_struct)

Format the time structure tm_struct in a flexible way using the format string fmt that contains ‘%’ substitutions similar to those in printf.

Except where noted, substituted fields have a fixed size; numeric fields are padded if necessary. Padding is with zeros by default; for fields that display a single number, padding can be changed or inhibited by following the ‘%’ with one of the modifiers described below. Unknown field specifiers are copied as normal characters. All other characters are copied to the output without change. For example:

strftime ("%r (%Z) %A %e %B %Y", localtime (time ()))
      ⇒ "01:15:06 AM (CST) Monday 17 February 1997"

Octave’s strftime function supports a superset of the ANSI C field specifiers.

Literal character fields:

%%: % character.
%n: Newline character.
%t: Tab character.

Numeric modifiers (a nonstandard extension):

- (dash): Do not pad the field.
_ (underscore): Pad the field with spaces.

Time fields:

%H: Hour (00-23).
%I: Hour (01-12).
%k: Hour (0-23).
%l: Hour (1-12).
%M: Minute (00-59).
%p: Locale’s AM or PM.
%r: Time, 12-hour (hh:mm:ss [AP]M).
%R: Time, 24-hour (hh:mm).
%s: Time in seconds since 00:00:00, Jan 1, 1970 (a nonstandard extension).
%S: Second (00-61).
%T: Time, 24-hour (hh:mm:ss).
%X: Locale’s time representation (%H:%M:%S).
%z: Offset from UTC (±hhmm), or nothing if no time zone is determinable.
%Z: Time zone (EDT), or nothing if no time zone is determinable.

Date fields:

%a: Locale’s abbreviated weekday name (Sun-Sat).
%A: Locale’s full weekday name, variable length (Sunday-Saturday).
%b: Locale’s abbreviated month name (Jan-Dec).
%B: Locale’s full month name, variable length (January-December).
%c: Locale’s date and time (Sat Nov 04 12:02:33 EST 1989).
%C: Century (00-99).
%d: Day of month (01-31).
%e: Day of month ( 1-31).
%D: Date (mm/dd/yy).
%h: Same as %b.
%j: Day of year (001-366).
%m: Month (01-12).
%U: Week number of year with Sunday as first day of week (00-53).
%w: Day of week (0-6).
%W: Week number of year with Monday as first day of week (00-53).
%x: Locale’s date representation (mm/dd/yy).
%y: Last two digits of year (00-99).
%Y: Year (1970-).

See also: strptime, localtime, gmtime, mktime, time, now, date, clock, datenum, datestr, datevec, calendar, weekday.

: [tm_struct, nchars] = strptime (str, fmt)

Convert the string str to the time structure tm_struct under the control of the format string fmt.

If fmt fails to match, nchars is 0; otherwise, it is set to the position of last matched character plus 1. Always check for this unless you’re absolutely sure the date string will be parsed correctly.

See also: strftime, localtime, gmtime, mktime, time, now, date, clock, datenum, datestr, datevec, calendar, weekday.

Most of the remaining functions described in this section are not patterned after the standard C library. Some are available for compatibility with MATLAB and others are provided because they are useful.

: clock ()

Return the current local date and time as a date vector.

The date vector contains the following fields: current year, month (1-12), day (1-31), hour (0-23), minute (0-59), and second (0-61). The seconds field has a fractional part after the decimal point for extended accuracy.

For example:

fix (clock ())
     ⇒ [ 1993, 8, 20, 4, 56, 1 ]

clock is more accurate on systems that have the gettimeofday function.

See also: now, date, datevec.

: date ()

Return the current date as a character string in the form DD-MMM-YYYY.

For example:

date ()
  ⇒ "20-Aug-1993"

See also: now, clock, datestr, localtime.

: etime (t2, t1)

Return the difference in seconds between two time values returned from clock (t2 - t1).

For example:

t0 = clock ();
# many computations later…
elapsed_time = etime (clock (), t0);

will set the variable elapsed_time to the number of seconds since the variable t0 was set.

See also: tic, toc, clock, cputime, addtodate.

: [total, user, system] = cputime ();

Return the CPU time used by your Octave session.

The first output is the total time spent executing your process and is equal to the sum of second and third outputs, which are the number of CPU seconds spent executing in user mode and the number of CPU seconds spent executing in system mode, respectively.

If your system does not have a way to report CPU time usage, cputime returns 0 for each of its output values.

Note that because Octave used some CPU time to start, it is reasonable to check to see if cputime works by checking to see if the total CPU time used is nonzero.

See also: tic, toc.

: is_leap_year ()

: is_leap_year (year)

Return true if year is a leap year and false otherwise.

If no year is specified, is_leap_year uses the current year.

For example:

is_leap_year (2000)
   ⇒ 1

See also: weekday, eomday, calendar.

: tic ()

: id = tic ()

: toc ()

: toc (id)

: val = toc (…)

Set or check a wall-clock timer.

Calling tic without an output argument sets the internal timer state. Subsequent calls to toc return the number of seconds since the timer was set. For example,

tic ();
# many computations later…
elapsed_time = toc ();

will set the variable elapsed_time to the number of seconds since the most recent call to the function tic.

If called with one output argument, tic returns a scalar of type uint64 that may be later passed to toc.

id = tic; pause (5); toc (id)
      ⇒ 5.0010

Calling tic and toc this way allows nested timing calls.

If you are more interested in the CPU time that your process used, you should use the cputime function instead. The tic and toc functions report the actual wall clock time that elapsed between the calls. This may include time spent processing other jobs or doing nothing at all.

See also: toc, cputime.

: pause ()

: pause (n)

Suspend the execution of the program for n seconds.

If invoked without an input arguments then the program is suspended until a character is typed.

n is a positive real value and may be a fraction of a second, for example:

tic; pause (0.05); toc
     -| Elapsed time is 0.05039 seconds.

The following example prints a message and then waits 5 seconds before clearing the screen.

disp ("wait please...");
pause (5);
clc;

See also: kbhit.

: days = datenum (datevec)

: days = datenum (year, month, day)

: days = datenum (year, month, day, hour)

: days = datenum (year, month, day, hour, minute)

: days = datenum (year, month, day, hour, minute, second)

: days = datenum ("datestr")

: days = datenum ("datestr", f)

: days = datenum ("datestr", p)

: [days, secs] = datenum (…)

Return the date/time input as a serial day number, with Jan 1, 0000 defined as day 1.

The integer part, floor (days) counts the number of complete days in the date input.

The fractional part, rem (days, 1) corresponds to the time on the given day.

The input may be a date vector (see datevec), datestr (see datestr), or directly specified as input.

When processing input datestrings, f is the format string used to interpret date strings (see datestr). If no format f is specified, then a relatively slow search is performed through various formats. It is always preferable to specify the format string f if it is known. Formats which do not specify a particular time component will have the value set to zero. Formats which do not specify a date will default to January 1st of the current year.

p is the year at the start of the century to which two-digit years will be referenced. If not specified, it defaults to the current year minus 50.

The optional output secs holds the time on the specified day with greater precision than days.

Notes:

Years can be negative and/or fractional.
Months below 1 are considered to be January.
Days of the month start at 1.
Days beyond the end of the month go into subsequent months.
Days before the beginning of the month go to the previous month.
Days can be fractional.

Caution: this function does not attempt to handle Julian calendars so dates before October 15, 1582 are wrong by as much as eleven days. Also, be aware that only Roman Catholic countries adopted the calendar in 1582. It took until 1924 for it to be adopted everywhere. See the Wikipedia entry on the Gregorian calendar for more details.

Warning: leap seconds are ignored. A table of leap seconds is available on the Wikipedia entry for leap seconds.

See also: datestr, datevec, now, clock, date.

: str = datestr (date)

: str = datestr (date, f)

: str = datestr (date, f, p)

Format the given date/time according to the format f and return the result in str.

date is a serial date number (see datenum) or a date vector (see datevec). The value of date may also be a string or cell array of strings.

f can be an integer which corresponds to one of the codes in the table below, or a date format string.

p is the year at the start of the century in which two-digit years are to be interpreted in. If not specified, it defaults to the current year minus 50.

For example, the date 730736.65149 (2000-09-07 15:38:09.0934) would be formatted as follows:

Code	Format	Example
0	dd-mmm-yyyy HH:MM:SS	07-Sep-2000 15:38:09
1	dd-mmm-yyyy	07-Sep-2000
2	mm/dd/yy	09/07/00
3	mmm	Sep
4	m	S
5	mm	09
6	mm/dd	09/07
7	dd	07
8	ddd	Thu
9	d	T
10	yyyy	2000
11	yy	00
12	mmmyy	Sep00
13	HH:MM:SS	15:38:09
14	HH:MM:SS PM	3:38:09 PM
15	HH:MM	15:38
16	HH:MM PM	3:38 PM
17	QQ-YY	Q3-00
18	QQ	Q3
19	dd/mm	07/09
20	dd/mm/yy	07/09/00
21	mmm.dd,yyyy HH:MM:SS	Sep.07,2000 15:38:08
22	mmm.dd,yyyy	Sep.07,2000
23	mm/dd/yyyy	09/07/2000
24	dd/mm/yyyy	07/09/2000
25	yy/mm/dd	00/09/07
26	yyyy/mm/dd	2000/09/07
27	QQ-YYYY	Q3-2000
28	mmmyyyy	Sep2000
29	yyyy-mm-dd	2000-09-07
30	yyyymmddTHHMMSS	20000907T153808
31	yyyy-mm-dd HH:MM:SS	2000-09-07 15:38:08

If f is a format string, the following symbols are recognized:

Symbol	Meaning	Example
yyyy	Full year	2005
yy	Two-digit year	05
mmmm	Full month name	December
mmm	Abbreviated month name	Dec
mm	Numeric month number (padded with zeros)	01, 08, 12
m	First letter of month name (capitalized)	D
dddd	Full weekday name	Sunday
ddd	Abbreviated weekday name	Sun
dd	Numeric day of month (padded with zeros)	11
d	First letter of weekday name (capitalized)	S
HH	Hour of day, padded with zeros,	09:00
	or padded with spaces if PM is set	9:00 AM
MM	Minute of hour (padded with zeros)	10:05
SS	Second of minute (padded with zeros)	10:05:03
FFF	Milliseconds of second (padded with zeros)	10:05:03.012
AM	Use 12-hour time format	11:30 AM
PM	Use 12-hour time format	11:30 PM

If f is not specified or is -1, then use 0, 1 or 16, depending on whether the date portion or the time portion of date is empty.

If p is nor specified, it defaults to the current year minus 50.

If a matrix or cell array of dates is given, a column vector of date strings is returned.

See also: datenum, datevec, date, now, clock.

: v = datevec (date)

: v = datevec (date, f)

: v = datevec (date, p)

: v = datevec (date, f, p)

: [y, m, d, h, mi, s] = datevec (…)

Convert a serial date number (see datenum) or date string (see datestr) into a date vector.

A date vector is a row vector with six members, representing the year, month, day, hour, minute, and seconds respectively.

f is the format string used to interpret date strings (see datestr). If date is a string, but no format is specified, then a relatively slow search is performed through various formats. It is always preferable to specify the format string f if it is known. Formats which do not specify a particular time component will have the value set to zero. Formats which do not specify a date will default to January 1st of the current year.

p is the year at the start of the century to which two-digit years will be referenced. If not specified, it defaults to the current year minus 50.

See also: datenum, datestr, clock, now, date.

: d = addtodate (d, q, f)

Add q amount of time (with units f) to the serial datenum, d.

f must be one of "year", "month", "day", "hour", "minute", "second", or "millisecond".

See also: datenum, datevec, etime.

: c = calendar ()

: c = calendar (d)

: c = calendar (y, m)

: calendar (…)

Return the current monthly calendar in a 6x7 matrix.

If d is specified, return the calendar for the month containing the date d, which must be a serial date number or a date string.

If y and m are specified, return the calendar for year y and month m.

If no output arguments are specified, print the calendar on the screen instead of returning a matrix.

See also: datenum, datestr.

: [n, s] = weekday (d)

: [n, s] = weekday (d, format)

Return the day of the week as a number in n and as a string in s.

The days of the week are numbered 1–7 with the first day being Sunday.

d is a serial date number or a date string.

If the string format is not present or is equal to "short" then s will contain the abbreviated name of the weekday. If format is "long" then s will contain the full name.

Table of return values based on format:

`n`	`"short"`	`"long"`
1	Sun	Sunday
2	Mon	Monday
3	Tue	Tuesday
4	Wed	Wednesday
5	Thu	Thursday
6	Fri	Friday
7	Sat	Saturday

See also: eomday, is_leap_year, calendar, datenum, datevec.

: e = eomday (y, m)

Return the last day of the month m for the year y.

See also: weekday, datenum, datevec, is_leap_year, calendar.

: datetick ()

: datetick (axis_str)

: datetick (date_format)

: datetick (axis_str, date_format)

: datetick (…, "keeplimits")

: datetick (…, "keepticks")

: datetick (hax, …)

Add date-formatted tick labels to an axis.

The axis to apply the ticks to is determined by axis_str which can take the values "x", "y", or "z". The default value is "x".

The formatting of the labels is determined by the variable date_format, which can either be a string or positive integer that datestr accepts.

If the first argument hax is an axes handle, then plot into this axes, rather than the current axes returned by gca.

See also: datenum, datestr.