Reading curve data
The easiest way to read curve data (x,y pairs) into VisIt is to create a curve file. A curve file consists of a header line that indicates the name of the curve, followed by 1 line of text per space-separated x,y pair. Here is an example file:
# xsquared 0.00000 0.00000 1.00000 1.00000 2.00000 4.00000 3.00000 9.00000 4.00000 16.00000 5.00000 25.00000
It is also possible to have more than one curve per file by repeating the above pattern in the file and providing different curve names and data.
Since VisIt uses file extensions to match files to database reader plugins, you should give your file a .curve,.ultra,.ult, or .u file extension to tell VisIt that your file is a Curve file.
 Curve data over time
The Curve file format does not permit multiple time steps. If you want to animate curve data, you will need to create separate curve files whose filenames look related. For example, you create files called: file0000.curve, file0001.curve, file0002.curve, ... and VisIt will group those files into a virtual database if the File Selection window has file grouping enabled. When you open a virtual database in VisIt, the animation controls will become active.
 Plotting curve data
Curve data can be plotted using the Curve plot. When you have opened a Curve file, the Curve plot menu will contain the names of the curves from your file. Just select a curve name to create a Curve plot of the variable and click the Draw button in the Main window.
 Manipulating curves
You can create new, derived curves in the Expressions window. For example, if you opened the data file from the above example, you could create a new Curve based on that data by creating a new expression and setting its type to Curve mesh variable. Rename the expression from untitled to something meaningful. Next, add a definition for the expression. Many of the operators in VisIt's expression language can operate on curves. You might want to add two curves together "a + b" or take the square root of the curve "sqrt(a)" and so on. The derived curves that you create via expressions also appear in the Curve plot's menu so they can be plotted as any other curves.
 Saving curve data
Once you have curve data in the visualization window, you may want to export that data for analysis in other applications. You can do that by first selecting the Curve plot that you want to save in the plot list and then by saving the window in "curve" format. You can do that by opening the Set save options window and by setting the file format to curve before saving the window.