|DataLab is a compact statistics package aimed at exploratory data analysis. Please visit the DataLab Web site for more information....|
|Home Introduction Guided Tour Playing with the data charts|
|See also: Plot Options, Plot Windows, Concepts behind DataLab, Basic Skills, Window, Fixed Labelling of Axes
Guided Tour: Playing with the data charts
For the first time let us do some playing with the windowing system of DataLab. Let us assume that DataLab is properly installed and can be started by clicking the DataLab icon in Windows. The start-up display of DataLab only shows the matrix viewer window and the numeric editor unless you have saved the results of the last session. On exit, DataLab stores the current configuration and reloads it when starting the next time. Thus you can continue at exactly the same point where you left DataLab.
In this example, we shall define a data table which consists of 100 rows and 4 columns. In order to get a common starting point we shall load the example data EXMPL-A.ASC as a template. This file contains artificial data stored in a table of 150 rows and 3 columns. The first column holds random values in the range of 0.0 to 10.0, the second column holds the cosine of the values of column 1, and the third column holds the square of column 1. Choose the command File/Load/ASC Format... and select the file 'EXMPL-A.ASC'.
A single window (the matrix viewer) will appear on the screen which shows a graphical overview of the data and give access to edit the table. The matrix viewer consists of several windows, one of these windows showing the matrix survey plot (click on the "Survey" tab if it not already open). This survey plot may look unfamiliar to you but is easy to understand. It gives you a bird's eye view of the data in your data matrix. Each value in the matrix is represented by a rectangle whose size is proportional to the value it represents. The rectangles are arranged just in the same way as the numeric values would appear on a printed version of the data matrix (matrix index runs from top to bottom and from left to right). When moving the mouse over the survey plot the cell coordinates and the contents of the addressed cell are displayed.
Next, we shall change the dimensions of the data table. This reconfiguration is done either by using the command Edit/Resize Data Matrix or by clicking the Resize button () in the matrix viewer. Now you have to enter the number of rows (100) and the number of columns (4). This can be done by using the arrows in the Resize window. After the number of rows and columns have been set click OK () to accept this setting. DataLab now sets up a new data table which holds the unchanged values in the part of the previous dimensions and zero values in the parts of the table which have been added by the definition of the new dimensions. This conservation of the old data makes it very easy to change the dimensions of the table without losing the data.
Next, we open a data window. Therefore either use the menu command Window/New, or the corresponding shortcut button (). DataLab thereafter displays a new data window. The contents of the windows can be changed by using the plot options and the navigation buttons at the left of the chart. The size of the chart can be changed by resizing the chart window.
In order to display a parcticular diagram, one has to set up the chart by clicking the setup button () of the chart window. As an example, let us display the values of a single column of the data matrix against their index. The type of the plot is indicated by the caption of the window. The default type is Col/Idx, which is exactly what we want. In order to change the type of the plot, click the setup button and select the kind of plot you want. In order to select a variable you have two choices: (1) you may click the arrows at the left side of the chart. Clicking the arrow to the left decrements the column (row) index, clicking the arrow to the right increments it. Try to change the displayed data column in our example by clicking the arrows for the y-axis. (2) you may select a variable directly by clicking the eye dropper button () in the chart window.
The data may be displayed using various viewing modes (points, lines, colors, etc.) which can be selected by using the plot options.
Now let's display another chart, which shows an x-y-plot. We open another window by clicking the command Window/New. This new window is configured to show an x-y-plot by using the setup button and selecting Col/Col as diagram type. Selecting the first and the second column of our data set (use the arrows to switch the axes) results in a plot of a cosine line established by irregularly spaced data points (since column 2 holds the cosine of the data in column 1 which are random points in the range of [0,10]). Try to have a look at all possible combinations of the three columns.