eloop

eloop(expr)

The eloop function is similar to the tloop function. When displaying a grads expression (expr) with the E (Ensemble) dimension varying, the eloop function will evaluate the exprwith each designated ensemble member fixed, then reassemble the grids to obtain a final result that is E-varying. The eloop function is provided as a way to obtain E-varying results from functions or expressions that are unable to operate when E is a varying dimension.

set cthick

This command sets the thickness for the contour lines.

Synatx

set cthick thickness

The thickness arg must be an integer in the range of 1 to 12 (or 256 for version 2.1 and later)

query

The query command allows the user to get information about a variety of aspects of the current grads session. Configuration, plot characteristics, graphics specifics, and file structure are some examples. The use of query pos combined with the coordinate transformations is the basis of many interactive applications with buttons and drop menus. The query command may be shortened to simply q. The syntax is:

query <option>
or
q <option>

set cterp

set cterp on|off

Turns spline smoothing on or off. "Sticks" until reset. Shaded contours are drawn without spline fitting, so to insure an exact match when overlaying contour lines and shaded contours of the same field, specify cterp as off. You can still use the csmooth option, which affects both contour lines and shaded contours.

set cstyle

set cstyle style

Sets the contour linestyle. style options are:

0 - no contours 
1 - solid 
2 - long dash 
3 - short dash 
4 - long dash, short dash 
5 - dotted 
6 - dot dash 
7 - dot dot dash 

set csmooth

set csmooth on|off

If on, the grid is interpolated to a finer grid using cubic interpolation before contouring. "Sticks".

Using grads Station Data

This section describes some of the grads commands and functions that are available for analyzing and displaying station data. Please refer to the companion section About Station Data for information on the structure of station data files, how to create them, and how to instruct grads to interpret them properly.

Here are some quick links for skipping through this section:

• Operating on Station Data
• Plotting Station Models
• Drawing Arbitrary Cross Sections

set coslat

set coslat on|off

Sets scaling of the Latitude dimension to be the cosine of latitude, producing a "crunched" effect near the poles. Will only work for 1-D plots in which Latitude (Y) is the varying dimension. Sticks until reset.

cos

cos(expr)

Takes the cosine of the expr. Values are assumed to be in radians. Works on both gridded and station data.

()tcorr

(tcorr (expr1, expr2, tdim1, tdim2

This function produces a spatial map of temporal correlation coefficients.

expr1   - a valid grads expression that varies in time
expr2   - a valid grads expression that varies in time and may also vary in X and Y
tdim1   - starting time dimension expression 
tdim2   - ending time dimension expression 

()scorr

This function calculates the spatial correlation between two variables over an X-Y domain. It returns a single number. The syntax is:

(scorr(expr1, expr2, xdim1, xdim2, ydim1, ydim2

Components of a grads Data Descriptor File

query

The query command allows the user to get information about a variety of aspects of the current grads session. Configuration, plot characteristics, graphics specifics, and file structure are some examples. The use of query pos combined with the coordinate transformations is the basis of many interactive applications with buttons and drop menus. The query command may be shortened to simply q. The syntax is:

()const

const (expr, value, <-u|-a>)

This is a powerful function that allows the user to change the missing values of a variable, set all the non-missing values of a variable to a constant, or set all possible values of a variable (both valid and missing) to a constant.

expr   a valid grads expression 
value  a constant, either an integer or floating point value 
-u     all missing data are set to value; non-missing data are unchanged
-a     all data are set to value, both missing and non-missing

query

The query command allows the user to get information about a variety of aspects of the current grads session. Configuration, plot characteristics, graphics specifics, and file structure are some examples. The use of query pos combined with the coordinate transformations is the basis of many interactive applications with buttons and drop menus. The query command may be shortened to simply q. The syntax is:

query <option>
or
q <option>

Reading and Writing Compressed Data Sets

Command line editing and history

If the readline library compiles on your system then the default prompt will be ga-> as opposed to ga>. This indicates that command line editing is active. The library defaults toemacs mode but can be set up to run using vi syntax.

Here's a list of the commands which may typically be used:

ctrl-a   go to beginning of line 
ctrl-e   go to end of line 
ctrl-f   go forward one char 
ctrl-b   go backward one char 
ctrl-d   delete the char 
ctrl-p   recall previous line
ctrl-n   recall next line
ctrl-r   reverse search

Controlling Colors in grads

The grads Default colors

	Col#  Description   Sample    R   G   B  



	 0   background  0   0   0 (black by default) 



	 1   foreground  255 255 255 (white by default) 



	 2   red  250  60  60  



	 

()coll2gr

This function creates a grid from a collection of station data. The syntax is:

(<coll2gr(cnum <,num

cnum     collection number
num      number of vertical levels in the output grid (default is 10)

collect

This command provides a way for station data profiles and time series to be saved in memory as a set. The command format is:

collect cnum expr

set cmin

set cmin value

Contours not drawn below this value. Reset by clear or display.

set cmax

set cmax value

Contours not drawn above this value. Reset by clear or display.

set cmark

set cmark marktype

Set the style of the marker for line plots, or for the gxout option 'stnmark'. marktype may be one of the following:

set clskip

set clskip number <spacing>

For example, set clskip 2 would label every other contour.

close

close the last descriptor file number for current file

set clopts

Syntax

set clopts color <thickness <size>>

set clip

set clip xlo xhi ylo yhi

This command sets the coordinates for clipping the plot area for display and draw commands. The four arguments xlo, xhi, ylo, yhi are the clipping coordinates in real page inches.

set clevs

set clevs lev1 lev2 lev3 ... levN

Sets specific contour levels.

clear

clear (or just c)

Issued without parameters, the clear command does pretty heavy duty clearing of many of the grads internal settings. Parameters can be added to limit what is cleared when using more advanced features.

set clab

set clab option

Controls contour labeling. The option argument may be one of the following:

on       'fast' contour labels are plotted where the contour lines are horizontal 
off      no contour labels 
forced   an attempt is made to label all contour lines 
format   gives a C-language template for conversion of the contour value to a string 
masked   (version 2.0.a6+) contour lines have gaps for the labels, so rectangles for label background are not drawn; contour labels never overlap.

set cint

set cint value

Sets the contour interval to the specified value. Reset by clear or display.

set chunksize

set chunksize Xsize Ysize <Zsize> <Tsize> <Esize>

It is not necessary to specify the chunk size for the Z, T, or E dimensions if you wish to use the default values.

Templating over ENSEMBLE

In version 2.0, with the introduction of the extra grid dimension for ensembles, support was also added for file templating over E. The sole substitution template is %e and the substitution string is the ensemble name, which is provided in the EDEF entry in the descriptor file. Note that the ensemble names are limited to 15 characters -- keep this limit in mind when designing your data directory structure and file naming conventions (or use symbolic links to create short aliases for longer filenames). If you are templating over the ensemble dimension, there can be only one ensemble member per file. If your data set has an ensemble dimension, and you are using templating over T but not E (i.e., there is no %e in the DSET entry), then all ensemble members are presumed to have identical time axes, and all members must be contained in the data file for a given time. Templating over T but not E is not supported for data sets in flat binary or GRIB1 formats.

cdiff

cdiff(expr,dim)

Performs a centered difference operation on expr in the direction specified by dim. The difference is done in the grid space, and no adjustment is performed for unequally spaced grids. The result value at each grid point is the value at the grid point plus one minus the value at the grid point minus one. The dim argument specifies the dimension over which the difference is to be taken, and is a single character: X, Y, Z, or T.

Result values at the grid boundaries are set to missing.

set ccols

set ccols col1 col2 col3 ... colN

Sets specific color numbers for contour levels specified by set clevs.

set ccolor

This command sets the color of the plotted contours.

Syntax

set ccolor rainbow | revrain
set ccolor color#

draw dropmenu

draw dropmenu number xpos ypos width height text_list

Draws a drop menu with the following attributes:

number       menu number, 0 - 64
xpos         x center of the menu base in page coordinates (inches)
ypos         y center of the menu base in page coordinates (inches)
width        width (x) of the menu base (inches)
height       height (y) of the menu base (inches)
text_list    the contents of the menu, seperated by vertical bars (|)

set cachesf

set cachesf num

The default cache scale factor is 1.