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Messages - Ron D.

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16
Tips and Tutorials / Setting custom ranges on axes
« on: May 06, 2015, 12:11:28 AM »
When a data file is read in, the range of each axis is automatically set at the minimum and maximum for that variable. Starting with Sliver version 1.2 it is possible to shift the range of any axis up or down at either the top or bottom. This also has the effect of shifting lines up or down along or even off that axis. You can shift a range by selecting an axis and either using the shifting options under the Axis menu or pressing the arrow keys:

  • Up Arrow: Decrease the top range, shifting the lines up at the top
  • Down Arrow: Increase the top range, shifting the lines down at the top
  • Left Arrow: Increase the bottom range, shifting the lines down at the bottom
  • Right Arrow: Decrease the bottom range, shifting the lines up at the bottom

If pressing the arrow keys shifts through the menus instead, press the ALT key and try again.

These operations change the range at the top or bottom by a 0.9 or 1/0.9 factor. Lines can be shifted right off either end of an axis if desired to zoom into an area of interest along an axis.

However, it may take time to shift lines along multiple axes, and in any event only specific ranges can be set because of the constant factors. However, there is a way to set the axis ranges to your particular values (maybe you want the same range for all of them). First, save the current Sliver session to a CSV file by selecting the File-->Save Session menu option and entering a filename ending in a .csv suffix. Then open that file with any text editor. You will see that the minimum and maximum ranges for each axis, in order, are given in the last lines of the file, separated by commas. Edit those values to the ranges you want, save the file, and select the File-->Restore Session to load it in again. Now the axes will have the ranges you entered.

Note that the format of each line is minimum,maximum regardless of whether the axis has been inverted. The complete format of saved session files is provided in Appendix C of the Sliver User's Manual if you would like to change other attributes of the plot either manually or programmatically.

Ron

17
Hi All,

If you have many datasets to load, particularly when there are repetitive tasks involved in Sliver such as selecting variables, brushing ranges of lines in different colors and perhaps hiding some brushes, and particularly when you want to set specific ranges on the axes, it may be useful to programmatically perform all these functions.

This can be done (and has been done by at least one user) with a script that writes each of your datasets and its Sliver configuration into a session file that can then be "restored" in Sliver. Session files are normally created through the File-->Save Session menu option and then restored through the File-->Restore Session menu option. However, the session file is simply a text file, and you can create your own custom session files for your data. The session file format for Sliver v1.2 is described in Appendix C of the Sliver v1.2 User's Manual. It includes not only the data but also the any selections, brushing or visible/hidden attributes for the data.

Another advantage of the session file is that the last n lines of it provide the minimum and maximum ranges of each axis (assuming there are n axes), so this allows you to customize the ranges as well. In fact, even without scripting it can be handy to save a session file and then edit the last n lines to whatever axis ranges you want before restoring it.

Ron

18
Announcements / Sliver v1.2 Released
« on: April 20, 2015, 07:14:51 PM »
Hi All,

Sliver v1.2 has just been released and is available at http://www.sliversoftware.com/download.htm.

This version has several improvements, including reading time data in hh:mm:ss or mm:ss format, shifting lines off-axis to spread out lines of interest, and other improvements. See the Version Change Log at http://www.sliversoftware.com/versionchangelog.htm or the User's Manual for more information. You can unzip the new version of Sliver into a new folder or overwrite the files in an existing folder. If you use a new folder, you can preserve your previous settings by copying the settings.txt file from the older folder into the new folder while Sliver is not running.

This version also includes fixes for the two bugs I reported earlier on this forum.

Ron

19
UPDATE: Sliver v1.4 now includes a menu option to select lines lying within a user-entered range along an axis.

If you know that you want to select lines on the PC plot that fall within a specific range on an axis (a specific range of a variable), you can turn on the "Show axes values while swiping" option in the Options-->Plot Settings menu. Then as you swipe across an axis the values at the top and bottom of the rectangular selection box are displayed at those locations. In this way you can swipe until you reach a starting or ending value that you want.

If you have specific values for both a maximum and minimum, you can combine two selections, one where you swipe up to the maximum and one where you swipe down to the minimum.  For example, if you want to select all lines in the range 25 to 100 on an axis, you can swipe up from somewhere between these values until you see an axis value of 100. Then you can press "Ctrl" to OR a new selection and swipe down from anywhere within the first selection until you see an axis value of 25. Then you have selected lines that have values from 25 to 100 on that axis.

Selections occur anywhere within a selection box, not just along axes. In fact, the ability to swipe lines between axes is one of the convenient features of Sliver. In this case this means that additional lines outside the desired range that angle upward or downward may pass through the selection rectangle if it is too wide, and they would also be selected. For that reason you should swipe very close to the axis. In fact, before you swipe you might zoom into the plot and pan to the axis you want to swipe so you can make the selection rectangle lie very closely along the axis when you swipe.

Ron

20
The menu option Plots-->New Transparent PC Plot opens a new window in which the current PC plot is displayed with a level of transparency set by the alpha value. (The Java Real-time Environment, or JRE, must be installed on your PC for this window to appear.) For a given number of polylines, there will be an alpha value below which the window will not show any lines at all. This might happen if you had previously reduced the alpha value when viewing a larger dataset.

If you don't see any polylines in this window, increase the alpha value until you do. Pressing the numbers 0 through 9 on the keyboard will assign an alpha value from 0.01 to 0.50, where 1.00 represents no transparency at all. Pressing the UP/DOWN arrows on the keyboard will fine-adjust these values. These controls, and those for changing the width of the polylines, are listed when pressing "h" to see the help in that window.

Ron

21
Tips and Tutorials / Locking a 2D scatterplot
« on: January 25, 2015, 11:22:12 PM »
Pressing "k" when a 2D scatterplot is the active window will "lock" the scatterplot in its current color scheme. The window title will indicate that it is locked. Selections cannot be made in a locked scatterplot, and any changes to the main PC plot or other scatterplots have no effect on it. This allows two or more scatterplots to be created that have different color brushing as a means of comparison.

Pressing "k" again when a locked scatterplot is the active window will unlock it, and it will automatically update to the color brushing of the PC plot and any other unlocked scatterplots.

Ron

22
Tips and Tutorials / Boolean operations when selecting lines or points
« on: January 25, 2015, 11:14:47 PM »
This is described in the User's Manual and the Help-->Tips menu, but just to be clear on this, after you select a group of lines in the PC plot or points in a 2D scatterplot, you can modify that selection as many times as you wish using Boolean operators:

- Press Ctrl while swiping to OR the new selection

- Press Shift while swiping to AND the new selection

- Press Ctrl-Shift while swiping to XOR the new selection

Also, you can choose the Brushes-->Toggle Selection to perform a NOT operation on the current selection. It is sometimes easier to select the lines you don't want and then toggle that selection rather than directly selecting the lines that you want.

Selection combinations can be performed in the PC plot or in any 2D scatterplots, in one or the other or mixed.

Ron

23
Tips and Tutorials / Range brushing only selected lines
« on: January 25, 2015, 10:52:18 PM »
Range brushing an axis of the PC plot consists of selecting that axis by clicking on its name while pressing ALT, and then either choosing the Axis-->Range Brush option or pressing "r" (sometimes you may have to press "r" twice). Two to eight brushes (colors) will be applied depending on the setting in the Options-->Plot Settings menu.

When no lines are selected, this clears all existing brushes. Then all lines are re-brushed in a spectrum from the bottom of the axis to the top of the axis. This is a very effective way to quickly show structural trends in the data, particularly when there is significant overplotting.

However, if any lines are selected when range brushing happens, only the selected lines will be range brushed. They are brushed in a spectrum in a range from the lowest selected line on that axis to the topmost selected line. All other lines are unbrushed. This allows the range brushing to be dependent on another variable or a Boolean combination of other variables.

For example, in the standard selection process you might first select all lines that pass through a given set or range of values on the Variable A axis, or perhaps those that pass through those values but not other sets of values on the Variables B and Variable C axes. Then you can select the Variable D axis and range brush it, and you range brush just those lines you are interested in, with the spectrum ranging from their minimum value to their maximum value of Variable D.

Ron



24
When you resize a plot window, you generally need to move the cursor from outside to inside the window to re-scale the plot inside that window to the new dimensions of the window. This is true whether you drag a corner of the window to resize it or click on the maximize/minimize icon in the upper right corner of the window. Sometimes the plot resizing will occur without realizing that your mouse has moved the cursor into the window, however, as it is natural to re-enter the window to do something with the plot.

If the plot does not resize, use the mouse to move the cursor outside the window and then back in. If this does not work, resize the window again and repeat the re-entry of the cursor. This may happen occasionally when you maximize the window to full-screen, as there is no "outside" to move the cursor in from.

Ron

25
When the dataset size is large, you may find that swiping with the mouse to select lines in the PC plot is slow to react. This will not happen in 2D scatterplots because points are faster to redraw than polylines.

In the Options-->Plot Settings menu you can choose to replace the mouse swiping function in only the PC plot with a mechanism where you click on the corner points of a selection box. When this option is set, you first click on one corner point and then click on the diagonally opposite corner. A selection box is immediately drawn. If you are not satisfied with this selection box, you can click a different second corner and the selection box is redrawn with this new corner. You can continue to click second corners until you are satisfied with the selection box, and then press Enter to accept it and select all lines passing through it. If you wish to click on a new first corner, press ESC to start over with the first corner.

Ron

27
I have collected a good number of articles and other references on the use of parallel coordinates for data visualization. I also have some articles on the use of the multidimensional Grand Tour. If you would like to have a look at them, please use the information from the Contact tab along the top of the main Sliver pages at http://www.sliversoftware.comto email me.

Ron

28
General Discussion / Other parallel coordinates software programs
« on: January 01, 2015, 04:52:31 AM »
Appendix A of the Sliver User's Manual provides a list of other free software programs that support parallel coordinate plots and are worth investigating. I specifically recommend having a look at Mondrian at http://www.theusrus.de/Mondrian/ for extremely large datasets of up to a million records, which Sliver simply can't handle.

The Appendix lists the similarities and differences between these other programs and Sliver. There are indeed significant differences in features I find noteworthy, which was ultimately the impetus for me to create Sliver.

Ron

29
Tips and Tutorials / Strategies for dealing with overplotting
« on: January 01, 2015, 03:47:08 AM »
Overplotting occurs when there are so many polylines in a PC plot that all you see is a mass that cannot be distinguished as individual lines. This is quite common and quite off-putting. As Alfred Inselberg, who invented the use of parallel plots for data visualization, wrote, "Do not let the picture intimidate you!" *

The very first thing I do is pick the variable of most interest in seeing relationships, select that axis (Alt-click on the name), and do an automatic range brush of that axis with the maximum number of colors (eight) as determined in the settings. This usually immediately transforms an incomprehensible plot into something that really shows overall behavior of the data. It is an astonishing transformation, really. I repeat this for other axes if needed, and then I start color brushing smaller groups of interrelated lines. The automatic "gap brushing" option applies up to 20 different color brushes to groups of lines separated by the largest gaps on an axis, and can also be useful to sort out data that exhibits important gaps.

You can start pruning away uninteresting polylines by zooming, panning, showing values at the axes on mouse-overs, and color-brushing and hiding lines of different colors. Selected (swiped) lines can then be saved to a new data file, and when this new file is opened the ranges of the axes are automatically adjusted to the new ranges of the variables, which spreads out the lines even more.

Often the interesting aspects of PC plots are not the lines but gaps between the lines! Look for outliers and small negative spaces that can differentiate groups of polylines for selection and color brushing.

Move axes into different positions, or better yet create the PC plot matrix, to view the polyline structure between different pairs of neighboring axes. Uncorrelated variables on neighboring axes creates a cluttered, random mass of line segments between them. Correlated variables on neighboring axes produce strong direct, reciprocal or enveloped line segments. By arranging axes to show correlations you will find that clutter in the plot gives way to interesting and revealing structures.

In addition, Sliver offers two ways of applying transparency (or alpha-blending) to plots, first by invoking a separate PC plot window with adjustable transparency and linewidths, and second by exporting the plots to PDF with a transparency assigned in the settings. The plots are rendered in vector form in the PDF, so zooming while viewing the PDF is very effective in seeing the inner structure of the PC plot.

* Inselberg, Alfred. Multidimensional Detective, 1997. Download from http://courses.ischool.berkeley.edu/i247/f00/readings/inselberg-ieee97.pdf

Ron

30
Tips and Tutorials / Keyboard hotkeys
« on: January 01, 2015, 03:16:07 AM »
A convenient listing of hotkey assignments for different windows is provided by the Help-->Tips menu option, also accessed by Ctrl-H. In the Grand Tour and Transparent PC Plot windows you can press H to view their hotkey assignments.

Ron

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