...
A filter function to extract a subset of its geopoints input using a second geopoints as criteria. The two input geopoints must have the same number of values. The resulting output geopoints contains the values of the first geopoints where the value of the second geopoints is non-zero. It is usefully employed in conjunction with the comparison operators :
...
freeze
...
=
...
filter(temperature,temperature
...
<
...
273.15)
...
The
...
variable
...
freeze
...
will
...
contain
...
a
...
subset
...
of
...
temperature
...
where
...
the
...
value
...
is
...
below
...
273.15
...
.
...
The
...
following
...
example
...
shows
...
how
...
to
...
plot
...
a
...
geopoints
...
set
...
with
...
different
...
colours
...
:
#
...
Filter
...
from
...
"temperature"
...
points
...
at,
...
above,
...
below
...
273.15
...
cold
...
=
...
filter(
...
temperature,temperature<273.15
...
)
zero
...
=
...
filter(
...
temperature,temperature=273.15
...
)
...
warm
...
=
...
filter(
...
temperature,temperature>273.15
...
...
#
...
Create
...
three
...
symbol
...
plotting
...
definitions
...
red
...
=
...
psymb(
...
symbol_colour
...
:
...
"red"
...
)
...
blue
...
=
...
psymb(
...
symbol_colour
...
:
...
"blue"
...
)
...
black
...
=
...
psymb(
...
symbol_colour
...
:
...
"black"
...
)
...
...
#
...
Plot
...
everything
...
plot(zero,black,cold,blue,warm,red)
...
geopoints
...
filter
...
(
...
geopoints,number
...
)
geopoints
...
filter
...
(
...
geopoints,list
...
)
A
...
filter
...
function
...
to
...
extract
...
a
...
subset
...
of
...
its
...
geopoints
...
input
...
using
...
model
...
levels
...
as
...
criteria.
- If
...
- the
...
- second
...
- argument
...
- is
...
- a
...
- number,
...
- the
...
- function
...
- extracts
...
- all
...
- the
...
- geopoints
...
- for
...
- which
...
- the
...
- level
...
- is
...
- equal
...
- to
...
- the
...
- number.
- If
...
- the
...
- second
...
- argument
...
- is
...
- a
...
- list
...
- of
...
- two
...
- numbers
...
- [n1,n2]
...
- ,
...
- the
...
- function
...
- extracts
...
- all
...
- the
...
- geopoints
...
- for
...
- which
...
- the
...
- level
...
- lies
...
- in
...
- the
...
- n1-n2
...
- interval.
geopoints
...
filter
...
(
...
geopoints,date
...
)
geopoints
...
filter
...
(
...
geopoints,list
...
)
A
...
filter
...
function
...
to
...
extract
...
a
...
subset
...
of
...
its
...
geopoints
...
input
...
using
...
dates
...
as
...
criteria.
- If
...
- the
...
- second
...
- argument
...
- is
...
- a
...
- date,
...
- the
...
- function
...
- extracts
...
- all
...
- the
...
- geopoints
...
- for
...
- which
...
- the
...
- date
...
- is
...
- equal
...
- to
...
- the
...
- one
...
- specified
...
- as
...
- the
...
- second
...
- argument.
- If
...
- the
...
- second
...
- argument
...
- is
...
- a
...
- list
...
- of
...
- two
...
- dates
...
- [d1,d2]
...
- ,
...
- the
...
- function
...
- extracts
...
- all
...
- the
...
- geopoints
...
- for
...
- which
...
- the
...
- date
...
- lies
...
- in
...
- the
...
- d1-d2
...
- interval.
geopoints
...
filter
...
(
...
geopoints,list
...
)
A
...
filter
...
function
...
to
...
extract
...
a
...
subset
...
of
...
its
...
geopoints
...
input
...
using
...
a
...
geographical
...
area
...
as
...
criteria.
The
...
second
...
argument
...
is
...
a
...
list
...
of
...
four
...
numbers
...
(lat/long
...
coordinates)
...
defining
...
a
...
geographical
...
area
...
-
...
[North,West,South,East]
...
.
...
The
...
function
...
extracts
...
all
...
the
...
geopoints
...
that
...
fall
...
within
...
the
...
specified
...
area.
geopoints
...
geopoints find ( fieldset,number,number )
A filtering function that returns a geopoints holding the grid points whose value is equal to the value of the first number. If a second number is given as the third argument it is a tolerance threshold and the geopoints will hold the grid points for which :
abs(data-value) <= threshold
geopoints geosort ( geopoints )
...
geosort ( geopoints )
Returns a new geopoints variable that contains the input geopoints sorted geographically from North to South (and West to East in points with the same latitude value, then by height, with lowest numerical values first).
geopoints
...
interpolate
...
(
...
fieldset,geopoints
...
)
Generates
...
a
...
set
...
of
...
geopoints
...
from
...
a
...
field.
...
The
...
first
...
parameter
...
must
...
contain
...
a
...
single
...
field.
...
The
...
field
...
is
...
interpolated
...
for
...
each
...
position
...
of
...
the
...
geopoints
...
given
...
as
...
a
...
second
...
parameter.
...
Where
...
it
...
is
...
not
...
possible
...
to
...
generate
...
a
...
sensible
...
value
...
due
...
to
...
lack
...
of
...
valid
...
data
...
in
...
the
...
fieldset,
...
the
...
internal
...
geopoints
...
missing
...
value
...
is
...
used
...
(this
...
value
...
can
...
be
...
checked
...
for
...
with
...
the
...
built-in
...
variable
...
geo_missing_value
...
or
...
removed
...
with
...
the
...
function
...
remove_missing_values
...
).
vector
...
latitudes
...
(
...
geopoints
...
)
Extracts
...
the
...
latitudes
...
of
...
all
...
the
...
geopoints
...
and
...
returns
...
them
...
as
...
a
...
vector..
vector
...
levels
...
(
...
geopoints
...
)
Extracts
...
the
...
heights
...
of
...
all
...
the
...
geopoints
...
and
...
returns
...
them
...
as
...
a
...
vector.
vector
...
longitudes
...
(
...
geopoints
...
)
Extracts
...
the
...
longitudes
...
of
...
all
...
the
...
geopoints
...
and
...
returns
...
them
...
as
...
a
...
vector.
geopoints
...
max
...
(
...
geopoints,geopoints
...
)
geopoints
...
min
...
(
...
geopoints,geopoints
...
)
Returns
...
the
...
geopoints
...
of
...
maximum
...
(minimum)
...
value
...
at
...
each
...
point.
...
Missing
...
values
...
retain
...
their
...
value
...
of
...
geo_missing_value.
geopoints
...
max
...
(
...
geopoints,number
...
)
geopoints
...
min
...
(
...
geopoints,number
...
)
Returns
...
the
...
geopoints
...
of
...
the
...
maximum
...
(minimum)
...
of
...
number
...
and
...
the
...
geopoints
...
value
...
at
...
each
...
point.
...
Missing
...
values
...
retain
...
their
...
value
...
of
...
geo_missing_value.
geopoints
...
max
...
(
...
geopoints,fieldsets
...
)
geopoints
...
min
...
(
...
geopoints,fieldsets
...
)
Returns
...
geopoints
...
of
...
maximum
...
(minimum)
...
of
...
the
...
geopoints
...
value
...
and
...
the
...
geopoints
...
value
...
at
...
each
...
grid
...
point
...
or
...
spectral
...
coefficient.
...
Missing
...
values,
...
either
...
in
...
the
...
fieldset
...
or
...
in
...
the
...
original
...
geopoints
...
variable,
...
result
...
in
...
a
...
value
...
of
...
geo_missing_value.
number
...
maxvalue
...
(
...
geopoints
...
)
number
...
minvalue
...
(
...
geopoints
...
)
Returns
...
the
...
maximum
...
(minimum)
...
value
...
of
...
all
...
geopoints
...
values.
...
Missing
...
values
...
are
...
bypassed
...
in
...
this
...
calculation.
...
If
...
there
...
are
...
no
...
valid
...
values,
...
then
...
nil
...
is
...
returned.
number
...
mean
...
(
...
geopoints
...
)
Computes
...
the
...
mean
...
of
...
the
...
geopoints.
...
Missing
...
values
...
are
...
bypassed
...
in
...
this
...
calculation.
...
If
...
there
...
are
...
no
...
valid
...
values,
...
then
...
nil
...
is
...
returned.
geopoints
...
offset
...
(
...
geopoints,number,number
...
)
geopoints
...
offset
...
(
...
geopoints,list)
Modifies
...
the
...
locations
...
of
...
a
...
set
...
of
...
geopoints
...
by
...
specified
...
amounts.
...
The
...
offsets
...
can
...
be
...
specified
...
either
...
as
...
two
...
separate
...
numbers
...
or
...
as
...
a
...
2-element
...
list.
...
The
...
original
...
geopoints
...
variable
...
is
...
unaffected;
...
the
...
functions
...
return
...
a
...
new
...
variable.
geopoints
...
polar_vector
...
(
...
geopoints,
...
geopoints
...
)
Combines
...
two
...
single-parameter
...
geopoints
...
variables
...
into
...
a
...
polar
...
vector
...
style
...
geopoints
...
variable.
...
The
...
first
...
represents
...
speed,
...
the
...
second
...
represents
...
direction.
...
Both
...
input
...
geopoints
...
variables
...
should
...
contain
...
the
...
same
...
number
...
of
...
points.
geopoints
...
remove_duplicates
...
(
...
geopoints
...
)
Returns
...
a
...
new
...
geopoints
...
variable
...
that
...
contains
...
just
...
one
...
instance
...
of
...
any
...
duplicate
...
geopoint.
...
Two
...
geopoints
...
are
...
considered
...
to
...
be
...
duplicates
...
of
...
each
...
other
...
if
...
the
...
files
...
have
...
the
...
same
...
format
...
and
...
the
...
points
...
have
...
the
...
same
...
coordinates,
...
height,
...
date,
...
time
...
and
...
values.
geopoints
...
remove_missing_values
...
(
...
geopoints
...
)
Returns
...
a
...
new
...
geopoints
...
variable
...
that
...
contains
...
just
...
the
...
non-missing
...
values
...
from
...
the
...
input
...
geopoints
...
variable.
...
A
...
geopoint
...
is
...
considered
...
to
...
be
...
missing
...
if
...
either
...
its
...
value
...
or
...
value2
...
members
...
are
...
missing.
geopoints
...
set_latitudes
...
(
...
geopoints,
...
number
...
or
...
vector
...
or
...
list
...
)
geopoints
...
set_longitudes
...
(
...
geopoints,
...
number
...
or
...
vector
...
or
...
list
...
)
geopoints
...
set_levels
...
(
...
geopoints,
...
number
...
or
...
vector
...
or
...
list
...
)
geopoints
...
set_dates
...
(
...
geopoints,
...
number
...
or
...
vector
...
or
...
list
...
)
geopoints
...
set_times
...
(
...
geopoints,
...
number
...
or
...
vector
...
or
...
list
...
)
geopoints
...
set_values
...
(
...
geopoints,
...
number
...
or
...
vector
...
or
...
list
...
)
geopoints
...
set_value2s
...
(
...
geopoints,
...
number
...
or
...
vector
...
or
...
list
...
)
Returns
...
a
...
geopoints
...
variable
...
with
...
either
...
its
...
latitude,
...
longitude,
...
level,
...
date,
...
time,
...
value
...
or
...
value2
...
component
...
modified.
All
...
these
...
functions
...
take
...
two
...
parameters:
...
first
...
one
...
must
...
be
...
a
...
geopoints
...
variable,
...
the
...
second
...
can
...
be
...
a
...
number,
...
a
...
vector
...
or
...
a
...
list
...
of
...
numbers.
...
If
...
a
...
number
...
is
...
given
...
then
...
all
...
the
...
corresponding
...
values
...
(latitude,
...
longitude,
...
level,
...
or
...
...)
...
are
...
replaced
...
by
...
the
...
given
...
value.
If
...
a
...
vector
...
or
...
list
...
is
...
given
...
as
...
the
...
second
...
parameter
...
then
...
the
...
corresponding
...
values
...
are
...
replaced
...
from
...
the
...
given
...
vector
...
or
...
list.
...
If
...
the
...
vector
...
or
...
list
...
is
...
shorter
...
than
...
the
...
geopoints
...
count
...
then
...
only
...
the
...
first
...
values
...
that
...
have
...
a
...
corresponding
...
value
...
in
...
the
...
vector
...
or
...
list
...
are
...
changed.
NOTE:
...
for
...
dates,
...
8
...
digit
...
integers
...
must
...
be
...
used.
...
If
...
the
...
list
...
contains
...
non-numbers,
...
then
...
a
...
missing
...
value
...
is
...
written
...
into
...
the
...
corresponding
...
geopoints
...
value.
geopoints
...
subsample
...
(
...
geopoints,
...
geopoints
...
)
Returns
...
a
...
geopoints
...
variable
...
containing
...
the
...
same
...
locations
...
(latitude,
...
longitude
...
and
...
height)
...
as
...
the
...
second
...
geopoints
...
variable,
...
but
...
whose
...
values
...
are
...
from
...
the
...
first
...
geopoints
...
variable
...
(or
...
a
...
missing
...
value
...
if
...
point
...
not
...
found
...
in
...
the
...
first
...
variable).
...
Note
...
that
...
the
...
resulting
...
geopoints
...
variable
...
is
...
sorted
...
in
...
the
...
same
...
way
...
as
...
performed
...
by
...
the
...
geosort()
...
function.
...
This
...
means
...
that
...
you
...
need
...
to
...
be
...
careful
...
if
...
performing
...
functions
...
between
...
the
...
results
...
of
...
a
...
subsample()
...
operation
...
and
...
another
...
geopoints
...
variable;
...
if
...
the
...
locations
...
in
...
the
...
two
...
geopoints
...
are
...
the
...
same,
...
then
...
you
...
should
...
geosort()
...
the
...
second
...
geopoints
...
beforehand.
You
...
can
...
use
...
function
...
remove_missing_values()
...
if
...
you
...
need
...
to
...
get
...
rid
...
of
...
the
...
missing
...
valued
...
points
...
in
...
the
...
returned
...
geopoints
...
variable.
number
...
sum
...
(
...
geopoints
...
)
Computes
...
the
...
sum
...
of
...
the
...
geopoints.
...
Missing
...
values
...
are
...
bypassed
...
in
...
this
...
calculation.
...
If
...
there
...
are
...
no
...
valid
...
values,
...
then
...
nil
...
is
...
returned.
vector
...
or
...
list
...
value
...
(
...
geopoints
...
)
Extracts
...
the
...
values
...
of
...
all
...
the
...
geopoints
...
and
...
returns
...
them
...
as
...
a
...
vector.
...
If
...
the
...
values
...
are
...
strings,
...
then
...
the
...
result
...
is
...
a
...
list
...
of
...
strings.
vector
...
value2
...
(
...
geopoints
...
)
Extracts
...
the
...
second
...
values
...
of
...
all
...
the
...
geopoints
...
and
...
returns
...
them
...
as
...
a
...
vector.
geopoints
...
xy_vector
...
(
...
geopoints,
...
geopoints
...
)
Combines
...
two
...
single-parameter
...
geopoints
...
variables
...
into
...
a
...
u/v
...
style
...
geopoints
...
variable.
...
Both
...
input
...
geopoints
...
variables
...
should
...
contain
...
the
...
same
...
number
...
of
...
points.