grdvector(1) GMT grdvector(1)
NAME
grdvector - Plot vector field from two component grids
SYNOPSIS
grdvector compx.nc compy.nc -Jparameters [ -A ] [ -B[p|s]parameters ]
[ -Ccpt ] [ -Gfill ] [ -I[x]dx[/dy] ] [ -K ] [ -N ] [ -O ] [ -P
] [ -Qparameters ] [ -Rregion ] [ -S[i|l]scale ] [ -T ] [
-U[stamp] ] [ -Wpen ] [ -Xx_offset ] [ -Yy_offset ] [ -Z ] [
-fflags ] [ -pflags ] [ -ttransp ]
Note: No space is allowed between the option flag and the associated
arguments.
DESCRIPTION
grdvector reads two 2-D grid files which represents the x- and y-compo-
nents of a vector field and produces a vector field plot by drawing
vectors with orientation and length according to the information in the
files. Alternatively, polar coordinate r, theta grids may be given
instead.
REQUIRED ARGUMENTS
compx.nc
Contains the x-components of the vector field.
compy.nc
Contains the y-components of the vector field. (See GRID FILE
FORMATS below.)
-Jparameters (more a|)
Select map projection.
OPTIONAL ARGUMENTS
-A The grid files contain polar (r, theta) components instead of
Cartesian (x, y) [Default is Cartesian components].
-B[p|s]parameters (more a|)
Set map boundary frame and axes attributes.
-C[cpt]
Use cpt to assign colors based on vector length. Alternatively,
supply the name of a GMT color master dynamic CPT [rainbow] to
automatically determine a continuous CPT from the gridas
z-range. If the dynamic CPT has a default range then that range
will be imposed instead. Yet another option is to specify
-Ccolor1,color2[,color3,a|] to build a linear continuous cpt
from those colors automatically. In this case colorn can be a
r/g/b triplet, a color name, or an HTML hexadecimal color (e.g.
#aabbcc ).
-Gfill Sets color or shade for vector interiors [Default is no fill].
-I[x]dx[/dy]
Only plot vectors at nodes every x_inc, y_inc apart (must be
multiples of original grid spacing). Append m for arc minutes or
s for arc seconds. Alternatively, use -Ix to specify the multi-
ples multx[/multy] directly [Default plots every node].
-K (more a|)
Do not finalize the PostScript plot.
-N Do NOT clip vectors at map boundaries [Default will clip].
-O (more a|)
Append to existing PostScript plot.
-P (more a|)
Select aPortraita plot orientation.
-Qparameters
Modify vector parameters. For vector heads, append vector head
size [Default is 0, i.e., stick-plot]. See VECTOR ATTRIBUTES for
specifying additional attributes.
-Rxmin/xmax/ymin/ymax[+r][+uunit] (more a|)
Specify the region of interest. Specify a subset of the grid.
-S[i|l]scale
Sets scale for Cartesian vector length in data units per dis-
tance measurement unit [1]. Append c, i, or p to indicate the
measurement unit (cm, inch,or point). Prepend l to indicate a
fixed length for all vectors. For Geographic data, give scale
in data units per km. Use -Si if it is simpler to give the
reciprocal scale in measurement unit per data unit or km per
data unit.
-T Means the azimuths of Cartesian data sets should be adjusted
according to the signs of the scales in the x- and y-directions
[Leave alone]. This option can be used to convert vector
azimuths in cases when a negative scale is used in one of both
directions (e.g., positive down).
-U[[just]/dx/dy/][c|label] (more a|)
Draw GMT time stamp logo on plot.
-V[level] (more a|)
Select verbosity level [c].
-Wpen Set pen attributes used for vector outlines [Default: width =
default, color = black, style = solid].
-X[a|c|f|r][x-shift[u]]
-Y[a|c|f|r][y-shift[u]] (more a|)
Shift plot origin.
-Z The theta grid provided contains azimuths rather than directions
(implies -A).
-f[i|o]colinfo (more a|)
Specify data types of input and/or output columns.
-p[x|y|z]azim[/elev[/zlevel]][+wlon0/lat0[/z0]][+vx0/y0] (more a|)
Select perspective view.
-t[transp] (more a|)
Set PDF transparency level in percent.
-^ or just -
Print a short message about the syntax of the command, then
exits (NOTE: on Windows just use -).
-+ or just +
Print an extensive usage (help) message, including the explana-
tion of any module-specific option (but not the GMT common
options), then exits.
-? or no arguments
Print a complete usage (help) message, including the explanation
of all options, then exits.
GRID FILE FORMATS
By default GMT writes out grid as single precision floats in a
COARDS-complaint netCDF file format. However, GMT is able to produce
grid files in many other commonly used grid file formats and also
facilitates so called apackinga of grids, writing out floating point
data as 1- or 2-byte integers. (more a|)
VECTOR ATTRIBUTES
Several modifiers may be appended to the vector-producing options to
specify the placement of vector heads, their shapes, and the justifica-
tion of the vector. Below, left and right refers to the side of the
vector line when viewed from the start point to the end point of the
segment:
+aangle sets the angle of the vector head apex [30].
+b places a vector head at the beginning of the vector path [none].
Optionally, append t for a terminal line, c for a circle, a for
arrow [Default], i for tail, A for plain arrow, and I for plain
tail. Further append l|r to only draw the left or right side of
this head [both sides].
+e places a vector head at the end of the vector path [none].
Optionally, append t for a terminal line, c for a circle, a for
arrow [Default], i for tail, A for plain arrow, and I for plain
tail. Further append l|r to only draw the left or right side of
this head [both sides].
+g-|fill turns off vector head fill (if -) or sets the vector head
fill [Default fill is used, which may be no fill].
+hshape sets the shape of the vector head (range -2/2). Default is
controlled by MAP_VECTOR_SHAPE [0].
+l draws half-arrows, using only the left side of specified heads
[both sides].
+m places a vector head at the mid-point the vector path [none].
Append f or r for forward or reverse direction of the vector [for-
ward]. Optionally, append t for a terminal line, c for a circle, or
a for arrow head [Default]. Further append l|r to only draw the
left or right side of this head [both sides]. Cannot be combined
with +b or +e.
+nnorm scales down vector attributes (pen thickness, head size) with
decreasing length, where vectors shorter than norm will have their
attributes scaled by length/norm [arrow attributes remains invariant
to length].
+oplon/plat specifies the oblique pole for the great or small cir-
cles. Only needed for great circles if +q is given.
+p[-][pen] sets the vector pen attributes. If pen has a leading -
then the head outline is not drawn. [Default pen is used, and head
outline is drawn]
+q means the input angle, length data instead represent the start
and stop opening angles of the arc segment relative to the given
point.
+r draws half-arrows, using only the right side of specified heads
[both sides].
+t[b|e]trim will shift the beginning or end point (or both) along
the vector segment by the given trim; append suitable unit. If the
modifiers b|e are not used then trim may be two values separated by
a slash, which is used to specify different trims for the two ends.
Positive trims will shorted the vector while negative trims will
lengthen it [no trim].
In addition, all but circular vectors may take these modifiers:
+jjust determines how the input x,y point relates to the vector.
Choose from beginning [default], end, or center.
+s means the input angle, length are instead the x, y coordinates of
the vector end point.
Finally, Cartesian vectors may take these modifiers:
+zscale[unit] expects input dx,dy vector components and uses the
scale to convert to polar coordinates with length in given unit.
EXAMPLES
To draw the vector field given by the files r.nc and theta.nc on a lin-
ear plot with scale 5 cm per data unit, using vector rather than stick
plot, scale vector magnitudes so that 10 units equal 1 inch, and center
vectors on the node locations, run
gmt grdvector r.nc theta.nc -Jx5c -A -Q0.1i+e+jc -S10i > gradient.ps
To plot a geographic data sets given the files com_x.nc and comp_y.nc,
using a scale of 200 km per data unit and only plot every 3rd node in
either direction, try
gmt grdvector comp_x.nc comp_y.nc -Ix3 -JH0/20c -Q0.1i+e+jc -S200 > globe.ps
SEE ALSO
gmt(1), gmtcolors(5), grdcontour(1), psxy(1)
COPYRIGHT
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.4.2 Jun 24, 2017 grdvector(1)
gmt5 5.4.2 - Generated Thu Jun 29 08:31:47 CDT 2017