gmt-fork/doc/rst/source/events_common.rst_

|No-spaces|

Description
-----------

Reads (*x*, *y*\ [, *z*] [, *size*], *time* [, *length*] [, *label*]) data from *table* [or standard
input] and plots how the symbol for each event should look for the specified *now* time.
The reason they may differ is that events may have different lengths and we may
wish to accentuate the symbol attributes in ways to draw attention to an event when
it first happens and perhaps tone it down after a while to reduce clutter and focus
on more recent events. Optionally, each symbol may have a label that can be displayed at the
same time or delayed with respect to the symbol. This module is typically used in conjunction with :doc:`movie`
where the implicit loop over time is used to call it over a time-sequence and
thus plot symbols as events unfold.

Required Arguments
------------------

.. _-J:

.. |Add_-J| unicode:: 0x20 .. just an invisible code
.. include:: explain_-J.rst_

.. _-R:

.. |Add_-R| unicode:: 0x20 .. just an invisible code
.. include:: explain_-R.rst_

.. |Add_-Rz| unicode:: 0x20 .. just an invisible code
.. include:: explain_-Rz.rst_

.. _-S:

**-S**\ *symbol*\ [*size*]
    Specify the symbol to use for the event.  Optionally, append symbol *size* with unit from
    (**c**\|\ **i**\|\ **p**\ ).  If no *size* is given then we read an event-specific size
    from the data file's third column (fourth if **-C** is used). **Note**: Not all the symbols that
    are available in :doc:`psxy` can be used here.  At the moment we only support the basic
    symbols and custom symbols; bars, vectors, ellipses, fronts, decorated and quoted lines cannot
    be specified.  Symbols sizes read from a data file will be assumed to be in the unit controlled
    by :term:`PROJ_LENGTH_UNIT` unless they have **c**, **i**, or **p** appended.  If you are only
    plotting labels then **-S** is not required.

.. _-T:

**-T**\ *now*
    Set the current plot time. The time shifts and increments set in **-E** are all relative to this
    current time.  If an absolute time is given you may need to  use :term:`TIME_UNIT` to indicate
    the unit of the values given in options like **-E** and **-L**.

Optional Arguments
------------------

.. |Add_intables| unicode:: 0x20 .. just an invisible code
.. include:: explain_intables.rst_

.. _-B:

.. include:: explain_-B.rst_

.. _-C:

**-C**\ *cpt*
    Use the *cpt* to convert *z* values given in the optional third column to assign symbol colors.

.. _-D:

**-D**\ [**j**\|\ **J**]\ *dx*\ [/*dy*][**+v**\ [*pen*]]
    Offset the text from the projected (*x*,\ *y*) point by *dx*,\ *dy*
    [0/0]. If *dy* is not specified then it is set equal to *dx*. Use
    **-Dj** to offset the text away from the point instead (i.e., the
    text justification will determine the direction of the shift). Using
    **-DJ** will shorten diagonal offsets at corners by
    sqrt(2). Optionally, append **+v** which will draw
    a line from the original point to the shifted point; append a *pen*
    to change the attributes for this line.

.. _-E:

**-Es**\|\ **t**\ [**+o**\|\ **O**\ *dt*][**+r**\ *dt*][**+p**\ *dt*][**+d**\ *dt*][**+f**\ *dt*][**+l**\ *dt*]
    Set the time knots for the **s**\ ymbol or **t**\ ext time-functions.  Append
    **+o** to shift the event start and end times by a constant offset (basically shifting
    the event in time by *dt*\ ; or use **+O** to only shift the start time, effectively shortening
    the duration of the event), **+r** to indicate the
    duration of the rise phase, **+p** to set the duration of the plateau phase, **+d**
    to specify the duration of the decay phase, and **+f** to set the duration of the
    fade phase.  These are all optional [and default to zero], and can be set separately for symbols and texts.
    If neither **s** or **t** is given then we set the time knots for both features. **Note**: The **+l** modifier is
    restricted to **-Et** and specifies an alternative duration (visibility) of the text [same duration as symbol].
    Furthermore, the **+p** and **+d** periods do not apply to text labels.  **Note**: The **-Et** option is
    required if you wish to plot labels [plot symbols only].

.. _-F:

**-F**\ [**+a**\ *angle*][**+f**\ *font*][**+j**\ *justify*][**+r**\ [*first*]\|\ **z**\ [*format*]]
    By default, event label text will be placed horizontally, using the primary
    annotation font attributes (:term:`FONT_ANNOT_PRIMARY`), and centered
    on the data point. Use this option to override these defaults by specifying up to three
    text attributes (font, angle, and justification) directly on the command line. Use **+f**
    to set the font (size,fontname,color), **+a** to set the angle, and **+j** to set the justification.
    Normally, the text to be plotted is the trailing text.  Instead, use **+r** to use the
    record number (counting up from *first* [0]) or **+z** to format incoming *z* values (requires **-C**)
    to a string using the supplied *format* [use :term:`FORMAT_FLOAT_MAP`].

.. _-G:

**-G**\ *fill* :ref:`(more ...) <-Gfill_attrib>`
    Set constant shade or color for all symbols.

.. include:: explain_-Jz.rst_

.. _-L:

**-L**\ [*length*\|\ **t**]
    Specify the length (i.e., duration) of the event.  Append a *length* if all events have the same length,
    append **t** if end-times instead of lengths are given in the file after the *time* column,
    or leave blank if lengths can be read from the input file after the *time* column.  If **-L** is not
    given we assume events have an infinite duration.

.. _-M:

**-M**\ **i**\|\ **s**\|\ **t**\ [*val1*]\ [**+c**\ *val2*]
    Modify the initial **i**\ ntensity, **s**\ ize magnification, or **t**\ ransparency of the symbol during
    the *rise* interval [1, 1, and 100, respectively].  Repeatable for the different attributes.
    Optionally, for finite-duration events you may append **+c** to set the corresponding terminal value
    during the coda [0, 0, 100, respectively].

.. _-Q:

**-Q**\ *prefix*
    Save the intermediate event symbols and labels to permanent files instead of removing them when done.
    Files will be named *prefix*\ _symbols.txt and *prefix*\ _labels.txt.

.. _-U:

.. include:: explain_-U.rst_

.. _-:

.. |Add_-V| unicode:: 0x20 .. just an invisible code
.. include:: explain_-V.rst_

.. _-W:

**-W**\ *pen*
    Specify symbol outline pen attributes [Default is no outline].

.. |Add_-bi| replace:: [Default is 3 input columns].
.. include:: explain_-bi.rst_

.. |Add_-di| unicode:: 0x20 .. just an invisible code
.. include:: explain_-di.rst_

.. |Add_-e| unicode:: 0x20 .. just an invisible code
.. include:: explain_-e.rst_

.. |Add_-f| unicode:: 0x20 .. just an invisible code
.. include:: explain_-f.rst_

.. |Add_-h| unicode:: 0x20 .. just an invisible code
.. include:: explain_-h.rst_

.. include:: explain_-icols.rst_

.. |Add_perspective| unicode:: 0x20 .. just an invisible code
.. include:: explain_perspective.rst_

.. include:: explain_-qi.rst_

.. include:: explain_colon.rst_

.. include:: explain_help.rst_

The meaning of time
-------------------

While normally the meaning of "time" (e.g., such as in the argument to **-T**)
is in fact the time of the phenomenon being plotted, it may also be any other monotonically
increasing quantity of convenience, such as elapsed time, model time, frame number, or other physical
quantities such as distance.  It all depends on the context of the movie.  The values
given for delays, fades, etc. in **-E** are assumed to be in the same unit as the
given *time* argument to **-T**.  Thus, if *time* is a monotonically increasing frame
counter then the values in **-E** and **-L** refer to number of frames.  A special
situation occurs when *time* is in fact actual calendar time given by date/clock markers.
Here, the unit of the arguments in **-E** and **-L** is determined by the :term:`TIME_UNIT`
setting [second].  You will need to specify the desired time unit that should be used when
interpreting your **-E** and **-L** arguments.  The example below for seismicity uses
actual earthquake times but we use days as the unit as second is too small.

The three time-functions
------------------------

Events typically have either a finite length, e.g., the temporal extent of
the reign of a particular monarch, or are infinite.  Here, infinite simply means
its length exceeds the temporal extent of the time we are plotting.  In a movie,
a basic representation of these events as points on a map would be to start plotting
the symbol when the event starts and then keep the symbol visible on all frames until the
event ends (or never stop plotting them in the infinite length case).  However, to draw
attention to the arrival of a new event we can temporarily change three attributes of
the symbol: Its size, color intensity, and transparency.  You can think of these three
attributes as functions of time.  For some option settings, figure below
illustrates how the symbol size may vary through the timespan of the movie.

.. figure:: /_images/psevents_size.*
   :width: 400 px
   :align: center

   Implied evolution of one symbol's size-variation as a function of time
   given the time-knots from **-Es** and the magnifications from **-Ms**.
   Here we temporarily magnify the symbol size five times before decaying
   to the intended size and eventually shrink it further down to a small
   size during the fade and coda phases.

Similarly, to draw attention to the newly arrived event you may want to whiten the color
temporarily; this can be done via the **-Mi** option and figure below
illustrates how intensity may vary accordingly.

.. figure:: /_images/psevents_intensity.*
   :width: 400 px
   :align: center

   Implied evolution of one symbol's color intensity as a function of time
   given the time-knots from **-Es** and the intensities from **-Mi**.  Here we
   seek to whiten the symbol during the event arrival, as well as darken it
   during a permanent code phase.

Finally, for finite events you may wish to either fade them out completely or
simply fade them to a constant but still visible transparency; this future stage
is referred to as the coda and levels can be specified via the **-Mt** option.
Figure below illustrates how transparency may vary through time.

.. figure:: /_images/psevents_transparency.*
   :width: 400 px
   :align: center

   Here we show how a symbol may go from being invisible to reaching full opaqueness
   at the event begin time, finally fading to a near-invisible stage after reaching
   its length.

While shown in these examples, the rise, plateau, fade, and coda periods are all optional
and can be selected or ignored as you wish via **-E**.  You can choose to specify any or none
of the three time histories.  By default the symbol size is constant, there is no intensity
variation, and all symbols are opaque.

If trailing text is plotted (i.e., by selecting **-Et**) then only the transparency time-function
is used and neither the plateau nor decay periods apply.  The appearance and disappearance of a
label is thus dictated by an initial (and optional) rise time (during which the label slowly
becomes fully visible), an normal period (where it remains visible), followed by the optional
fade period (where the text fades out).  The figure below illustrate the setup:

.. figure:: /_images/psevents_labels.*
   :width: 400 px
   :align: center

   Here we show how a label may go from being invisible to reaching full opaqueness
   at the event begin time, staying visible for the given duration, and then finally
   fade away completely. For labels, the plateau and decay periods do not apply.



Sorting the data
----------------

While only the events that should be visible will be plotted at the given time set via **-T**,
the order of plotting is simply given by the order of records in the file.  Thus, if the
file is *not* sorted into ascending time then later events might plot *beneath* earlier events.
To prevent this, you can sort your file into ascending order via the :doc:`gmtconvert` **-N** option.