This function allows its user to define events with mouse clicks on
the current plot via the locator
function. The
arguments n
and type
are the usual parameters of the
locator
function. If EID
is not missing, then
n = length(EID)
.
On exit from locator
, suppose the user defined m
events. If EID
was missing, then the output data frame will
contain m events. However, if EID
exists, then the
output data frame will contain length(EID)
events, and both
X
and Y
will be NA
for events
EID[(
m+1):n]
. The na.omit
function
can remove rows with NA
s.