VCS Example: Modifying Common Graphics Method Attributes     


Description

Many different graphics methods are available in VCS (e.g., Boxfill,Isofill, Isoline, Outfill, Scatter, Vector, etc.). By using the appropriate editor panel, each graphics method can be modified to meet specific user needs. This example shows how to modify only the first 15 attributes that are common to all the graphics methods; modification of other attributes will be illustrated by subsequent examples. Note, in the present example the Boxfill graphics method is used for purposes of illustration.

Step 1: Modifying the Boxfill Attribute Set

Access the blue Boxfill Graphics Method Panel (via Main Menu: `Primary' -> `Graphics Table' -> Boxfill). Note, because VCS does not allow the modification of any `default' attribute sets, another name must be assigned. Therefore, move the pointer over the Boxfill `default' attribute set name and click the middle mouse button. Next, move the pointer over the Boxfill menu button and press and hold the left mouse button. Then move the pointer over the `Copy' item and release the left mouse button--a popup window will appear. Enter a new Boxfill attribute set name (e.g., `example') and select the `Save' button. This is the new Boxfill attribute set that will be modified in this example.

Use this newly created Boxfill attribute set name and the Template `default' attribute set name in the chosen picture descriptor form. Also use the variable `tas' in the example netCDF data file example.nc for display by the Boxfill graphics method on the VCS Canvas. (See the Example on Creating Plots by Different Graphics Methods).

Step 2: Accessing the Boxfill Editor Panel

In the blue Boxfill Graphics Method Panel, scroll the window down until the `example' string is visible. Then select `example' with the left mouse button. (If `example' is selected with the middle mouse button, VCS will copy `example' into its copy buffer; if `example is selected with the right mouse button, VCS will delete `example' from the list.) The Boxfill Editor Panel (see above figure) will appear below. Scroll this panel to the bottom.

Step 3: Changing the Map Projection

Change the map projection by moving the pointer over the `projection' menu button in the Boxfill Editor Panel and pressing and holding the left mouse button. Then move the pointer over the desired map projection (e.g., `Mollweide') and release the left mouse button. Select the red `Apply' button to register changes. Then restore the map projection to `Linear'.

Note, the placement of segments such as the labels and tick marks is not addressed in this example. These attributes are changed by means of the Template Panel--see the Example on Modifying a Template. Note also, use of the spherical projections requires that the data be on a `longitude' by `latitude' grid--i.e., in the Data Editor Panel `xname' must be `longitude' and `yname' must be `latitude'. Moreover, when using the `Polar' projection, to center the map about the opposite pole it is necessary to exchange the `yfirst' and `ylast' values by use of the Data Editor Panel--see the Example on Modifying Data.

Step 4: Setting a List Name for Labels and Tick Marks

Remove the asterisk `*' from the `xticlabels#1' input text window (see above figure). Then select the red `Apply' button to register these changes. The x-axis labels and tick marks will be removed.

Next, access the List Table Panel (via Main Menu: `Basic' -> `List Table'). Note, because VCS does not allow the modification of the List `lon30' and `lat20' default attribute sets, these must be assigned new names. Therefore, select the List `lon30' attribute set name with the middle mouse button. Then move the pointer over the List menu button, press and hold the left mouse button, choose menu item `Copy' and release the left mouse button--a popup window will appear. Enter a new List attribute set name here (e.g., `example') and select the `Save' button. This is the new List attribute set that will be modified.

To do so, copy and drop the List `example' attribute set name into the `xticlabels#1' input text window, and select the red `Apply' button to register changes. The x-axis labels and tick marks will be shown with `W' and `E' appearing after the longitude values. Then select the List `example' attribute set name in the yellow List scroll panel--the List Editor Panel will appear below. Scroll the window down until the `0' (zero) value is visible, then edit the `String' side of the `0' value by entering `Equator'. Select the red `Apply' button to register the changes--the word `Equator' will appear as an x axis label. The labels and tick marks `xticklabels#2', `xmtics#1', `xmtics#2', `yticlabels#1', `yticlabels#2', `ymtics#1' and `ymtics#2' can be modified in the same manner.

See also Hints on the Boxfill Editor Panel for more information on modifying labels and tick marks.

Step 5: Defining Data Space in Real-World Coordinates

For the x-axis range on the VCS Canvas, set `datawc_x1' and `datawc_x2' in the Boxfill Editor Panel to values within that range (e.g., if x-axis range is -180 to 180, set new values -100 to 100). (Note, if `datawc_x1', `datawc_x2', `datawc_y1' or `datawc_y2' has a value of `1e+20', then VCS will use the data's coordinate specified in the Dimension Manipulation Panel. That is, if either `datawc_x1' or `datawc_x2' is set to `1e+20', then no change will take place.) Then do the same for the `datawc_y1' and `datawc_y2' values in the Boxfill Editor Panel. (Note, it is left up to the user to preserve the aspect ratio--e.g., 2:1 .) If the chosen coordinate values fall outside the actual data range, no data will appear.

See also Hints on the Boxfill Editor Panel for more information on defining the data space in real-world coordinates.

Step 6: Changing the X- and Y-Axis Values

Before working on the remainder of this step, transpose the 'X-longitude' and 'Z-time' dimensions to obtain 'X-time', 'Y-latitude', and 'Z-longitude'--see Step 11 of the Example on Modifying Data for instructions.

Next, change the x-axis values on the VCS Canvas by scrolling the Boxfill Editor Panel down until the label `xaxisconvert' is visible. Then move the pointer over the pulldown menu button (showing `linear') and press and hold the left mouse button. Five options for converting the x-axis will appear: `linear'; `log10', for log base 10; `ln', for natural log; `exp', for exponential; and `area_wt', for area-weighted. Move the pointer over `log10' and release. Then select the red 'Apply' button at the top of the Boxfill Editor Panel to register the changes on the VCS Canvas. (Note: if the map projection menu button is not set to 'Linear', then `xaxisconvert' and `yaxisconvert' will automatically default to `linear'.)

To view the border lines and the x- and y-tick marks, toggle the 'On/Off/Err' status button in the page descriptor form.

See also Hints on the Boxfill Editor Panel for more information on setting the X- and Y-axis values.



Last update December 12, 1996. For further information, contact: Dean N. Williams (vcs@pcmdi.llnl.gov)
This page is maintained by Anna McCravy (mccravy@pcmdi.llnl.gov)
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