The Basics

This chapter describes some of the elementary operations you can perform with XYPLOT. Advanced topics are covered in the subsequent chapters.

Getting Started

Linux or DOS: XYPLOT is started by typing one of these commands and pressing Enter.

to start the program and display a directory of files


xyplot filename
to start the program and plot filename

Windows: The recommended method for starting XYPLOT under Windows is by clicking on the xyplot shortcut on your desktop. Alternatively, you can start XYPLOT from a DOS Prompt or Command Prompt window by typing:

xyplot filename1 filename2 ...

If you are using the command prompt, be sure to start xyplot from its installation directory (typically C:\xyplot) so that xyplot can read its initialization file, xyplot.4th. If you include one or more filenames on the command line, XYPLOT will read the file(s) and then graph the data in the file(s).

Selecting a File

DOS: When you startup xyplot or choose Load from its file menu, the following prompt will be displayed:

Select the file >>

Type the name of the file you want to load and press Enter.

Windows: Click on the File menu and select Open. Select a file to load by navigating the standard File Open dialog box. Note that only files with extension DAT are listed. You can change the type of files which are displayed from a list in the dialog box.

A Guide to the Plot Display

A plot of the data in the file that you have selected appears on the plot display. Look at the following image for

Each of these has a special function. As much space as possible on the screen is allocated to the plot so that the data will be displayed at high resolution. Data is plotted within the plot window. When new data are loaded, the limits will be adjusted automatically to show you the entire plot, however, you may change the limits with the mouse, or through the menu.

A frame, its inner edges marked with fixed tics, surrounds the plot window. A dotted grid may be superimposed on the frame. The grid is toggled on or off by the G key. In this sense the plot display behaves as a piece of graph paper that sets the scales on its axes automatically to show the data that you have.

Setting the Plot Window Limits

XYPLOT automatically sets the plot window limits from the minimum to the maximum values in all the data. You may specify new window limits by

The first method is a quick way to get an expanded view of a region of interest. You can inspect fine detail in whatever region interests you. The second method sets the limits precisely. It is useful because in XYPLOT the x limits of the plot window also serve to select data for operations such as storing parts of a dataset, calculating areas, or making a polynomial fit. This is in analogy to selecting text for editing in a word processing program.

Setting Window Limits With the Plot Cursor

You may zoom in on part of the plot by using the mouse to define a box. Move the cursor to point at the lower left corner of a region you want to see in more detail. Hold down the left mouse button and move the mouse to define the box. Release the button and the graph will be redrawn with the new window limits. The portion of the plot window that had been inside the box will now fill the entire plot window.

Setting the Window Limits by Input

Press the E key and you will be prompted for the new window limits with a line reading:

Enter new window limits x1, y1, x2, y2:

where (x1, y1) is the lower left corner and (x2, y2) is the upper right corner of the window. You need not specify all of the new coordinates. For example, to change only y1 and y2, you could enter


Cancelling the Limits

Every time you change the window limits XYPLOT makes a record of the previous window limits.

DOS: Up to four levels of expansion are kept in memory.

To return to the previous level, press Esc.