Chapter 5. The Basics of Plot Manipulation
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# Chapter 5. The Basics of Plot Manipulation

Now that you are comfortable with creating plots in KST, we can explore some of the plot manipulation features available through the KST graphical user interface. Start KST from the command-line with the `mykstsession.kst` file you saved earlier:

    kst mykstsession.kst

All the plots you created earlier should now be loaded in KST. Examine the plot with the y axis label of `PSD of Column 2 (V/Hz^{1/2})`. To take a closer look at the plot, right click on it and select the Maximize menu item, as shown below:

The plot is now maximized within the current window. Note that anything beyond about 4 Hz does not look interesting in this plot, so it would be useful to view only the area of the plot that looks interesting. To do so, make sure you are in XY Mouse Zoom mode (select XY Mouse Zoom from the Plots menu, or click the toolbar button). Then, simply drag a rectangle from approximately (4, 0.025) to (0,0), as shown below. Note that the coordinates of the mouse cursor are displayed in the lower right corner of the KST window (if they are not, ensure that Show Statusbar is checked in the Settings menu).

The plot axes will change to “zoom in” on the selected area of the plot. You may notice that there is a peak at the left end of the power spectrum that extends beyond the new upper y axis limit. Suppose that you wish to view the top of this peak. Right-click on the plot and select Up from the Scroll submenu. The plot should scroll upwards. Of course, it is most likely easier to use the shortcut key associated with the menu item this is true for most of the zooming and scrolling functions. In this case, the shortcut key is Up Arrow, so the quickest way to scroll upwards would be to hold down the Up Arrow key. To return to maximum zoom at any time, right-click on the plot and select Zoom Maximum from the Zoom submenu (or type M, the shortcut key associated with Zoom Maximum).

Restore the size of the power spectrum plot by right-clicking the plot and unchecking Maximize.

Now look at the plots with y axes labelled `Column 2` and `Column 3`. These are plots of the pitch gyro and roll gyro, respectively, from the 1998 BOOMERANG flight. Since these two plots are related, it can be useful to zoom and scroll them simultaneously. Click on the squares located at the top right corners of the two plots. They should turn dark in colour to indicate that the two plots are now tied together:

Before we try zooming in, we should delete all plots other than the two we are working with. Select Layout Mode from the Plots menu or click the toolbar button. For each plot other than the two we want to keep, right-click on the plot and select Delete. Then, right-click anywhere inside the current window and select Cleanup Layout. Now the two plots should share maximal space inside the window. Return to XY Mouse Zoom mode when you are done.

Now try zooming in on any portion of the upper plot. You will find that the lower plot will become blank. This is because the lower plot axes have changed to match the upper plot axes, and there is no data in that particular region of the lower plot. Type M while the mouse cursor is over either plot to return to maximum zoom on both plots. Now hold down Ctrl (this is equivalent to selecting X Mouse Zoom Mode from the Plots menu or clicking the toolbar button). The mouse cursor will change shape as visual feedback. While keeping Ctrl held down, drag a rectangle in the upper plot. Note that the height of the dotted rectangle is restricted so that only the x axis will be zoomed. Now both plots will display data when zoomed in, as the y axis for either plot was not changed.

### Tip

You can quickly tie or untie all the plots in the window by selecting Tied Zoom from the Plots menu or by clicking the toolbar button.

When you are finished experimenting with the zooming features, you can close KST. There is no need to save the plots this time (unless you wish to).

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