subsetcircle             package:ssBase             R Documentation

_C_i_r_c_u_l_a_r _S_u_b_s_e_t _o_f _E_v_e_n_t_s

_D_e_s_c_r_i_p_t_i_o_n:

     Selects events within a specified circular selection criteria from
     given catalogue. Note that 'subset.circle' is deprecated; it
     conflicts with the generic function 'subset'. Change to
     'subsetcircle'; it has the same arguments.

_U_s_a_g_e:

     subsetcircle(x, centrelat=0, centrelong=0, minradius=0, maxradius=Inf,
                  mindepth=0, maxdepth=Inf, minmag=-Inf, maxmag=Inf,
                  minday=-Inf, maxday=Inf, radius=6371,
                  report.count=TRUE, na.rm=TRUE, ...)

     #   Deprecated Usage:
     subset.circle(x, centrelat=0, centrelong=0, minradius=0, maxradius=Inf,
                   mindepth=0, maxdepth=Inf, minmag=-Inf, maxmag=Inf,
                   minday=-Inf, maxday=Inf, radius=6371,
                   report.count=TRUE, na.rm=TRUE, ...)

_A_r_g_u_m_e_n_t_s:

       x: catalogue name. 

centrelat: latitude of the circle centre. Specified as degrees north
          (positive) or south  (negative) of the equator (-90 to 90). 

centrelong: longitude of the circle centre. Specified as degrees east
          of Greenwich (0 to  360). 

minradius: surface arclength radius (km) within which events are not to
          be selected. 

maxradius: surface arclength radius (km) within which events to be
          selected. 

mindepth: minimum depth in kilometres. 

maxdepth: maximum depth in kilometres. 

  minmag: minimum magnitude. 

  maxmag: maximum magnitude. 

  minday: the number of days (and fractions) after 00:00 hrs on 1
          January 1970 from which  events are required. See Details. 

  maxday: the number of days (and fractions) after 1 January 1970
          denoting the upper bound  of the time interval containing the
          required events. See Details. 

  radius: the assumed radius of the earth. Default is 6371 km. 

report.count: Boolean. Report the number of events referred to by the
          new subset.  Default is  'TRUE'. 

   na.rm: Boolean. Determines whether those events with missing values
          of the subsetting variables should be excluded, see Details. 
          Default is 'TRUE'. 

     ...: other options for restricting Catalogue data. These must take
          the form  'option == value', where 'option' is a component of
          the specified  catalogue. 

_D_e_t_a_i_l_s:

     The subsetting is based on the catalogue variables 'latitude',
     'longitude', 'depth', 'magnitude' and 'time'. The default settings
     for each of these variables is to take all events. The function
     only works through each of the "min" and "max" values _included in
     your function call_. Those arguments _not explicitly listed will
     have no effect_. A logical vector is constructed with the same
     length as the number of events in the catalogue, and indicates
     whether a given event satisfies the subsetting criteria. From
     this, the vector of indices of the required events is created.

     Historical events often have missing values, particularly the
     magnitude and depth. Consider the situation where 'minmag=6'. The
     logical vector within the function will contain 'TRUE''s and
     'FALSE''s for those events that satisfy or not satisfy this
     condition, respectively. However, for those historical events with
     a missing magnitude ('NA'), the elements in the logical vector
     will also be 'NA'. The argument 'na.rm' determines whether these
     events should be removed ('TRUE') or included ('FALSE') in the
     subset. The default setting is to remove such events, though in
     the context of large historical events, it would be more sensible
     to include them, i.e. 'na.rm=FALSE'.

     The arguments 'minday' and 'maxday' represent the boundary
     _points_ of the time interval, and can represent fractions of
     days. For example, 00:00 hrs on 1 Jan 1970 is represented as
     'minday=0', whereas 18:00 hrs on 2 Jan 1970 is represented as
     'minday=1.75'. Similarly, 18:32:24 hrs on 30 Sept 1990 could be
     specified as 'minday = julian(9,30,1990) + 18/24 + 32/(24*60) +
     24/(24*60*60)'. Note that 'maxday = julian(1,1,1990)' represents
     the _point_ 00:00 hrs on 1 Jan 1990, and therefore will not
     include events on 1 Jan 1990 after midnight.

_V_a_l_u_e:

     Returns an object of type list with class '"subset"'. All optional
      arguments above, except radius, are included as elements within
     the list. Other  components within the list are:

 indices: an array of indices for events in catalogue 'x' satisfying
          the selection criteria. 

 catname: catalogue name. 

    type: type of subset, set to '"Circular"'. 

_S_e_e _A_l_s_o:

     'subsetpolygon', 'subsetrect',  'subsetsphere', 'print.subset', 
     'summary.subset'

_E_x_a_m_p_l_e_s:

     #   Select events from the NZ55 catalogue, no more than
     #   100kms from Wellington.

     data(NZ55)
     a <- subsetcircle(NZ55, centrelat=-41.3, centrelong=174.8, 
                        maxradius=100)
     print(summary(a))

