Parallel Coordinate Plot Mode

This function is very similar to Find Similar. Instead of pressing and dragging a mouse cursor to select a seed profile, it allows you to select profiles of a certain color as seeds. Using the PCP in the above right panel as an example, invoking this function will first pop up a color selector like the following:

This function is not active and is grayed out in a right-click menu when all profiles in a PCP are of the same color.

This operation allows you to pick a few seed profiles with a cursor. One of the seed profiles is chosen as the current seed profile. The current seed profile is used as a guideline to construct an envelope. Only observation profiles within the specified envelope are displayed.

Use Figure 9-13 and the 3 observation profiles highlighted in black to illustrate this operation. The dialog generated by this operation with the 3 selected seed profiles is the left panel of Figure 9-16. The right panel is a snapshot of the left panel after the black envelope being adjusted.

Figure 9-16. Find Similar in Ranges dialogs

---> images/pcp-mode-find-similar-in-ranges-initial.png <--- ---> images/pcp-mode-find-similar-in-ranges-final.png <---

Properties of Find Similar in Ranges dialogs are:

• The seed panel:

  • One of the seed profiles is used as a guideline in the envelope panel to specify an envelope and it is called the current seed profile.

  • The current seed profile is drawn in its original color. All other seed profiles are drawn in less saturated colors of the same hue as their original colors.

  • Click the left mouse button while the cursor is over a seed profile to make it current.

  • Its right-click menu supports the following operations:

    • Copy

    • Identify... : The hand cursor is always black and profiles pointed by the hand cursor are highlighted in black.

    • Save as PNG Image...

    • Set Background...

• The envelope panel:

  • The current seed profile is drawn in its original color to provide a guideline for specifying an envelope.

  • There are 2 envelopes. One consists of 2 connected gray line segments; the other consists of 2 connected black line segments. The gray envelope goes through the minimum and the maximum data values at each axis. The black envelope is adjustable by you and and can be positioned anywhere inside of the gray envelope.

  • When the cursor, , is close to a knot on the black envelope, a red circle centered at the knot will be drawn:

    

    ---> images/pcp-mode-knot-ready.png <---

  • When a red circle is drawn around a knot on the black envelope, you can press the left mouse button and drag it up and down to adjust the black envelope, as illustrated by this image:

    

    ---> images/pcp-mode-knot-moving.png <---

    Notice that the cursor switches from to while the black envelope is being adjusted,

  • Its right-click menu supports the following operations:

    • Adjust Bound: 10% :

      Make the black envelope cover the central 10% of the data range at each axis.

    • Adjust Bound: 20% :

      Make the black envelope cover the central 20% of the data range at each axis.

    • Adjust Bound: 30% :

      Make the black envelope cover the central 30% of the data range at each axis.

    • Adjust Bound: 40% :

      Make the black envelope cover the central 40% of the data range at each axis.

    • Adjust Bound: 50% :

      Make the black envelope cover the central 50% of the data range at each axis.

    • Copy

    • Save as PNG Image...

    • Set Background...

    • Update in Real Time:

      The action of this menu item depends on if there is a ✓ mark to its left in the right-click menu. If there is no ✓ mark, selecting this menu item will case the result panel to update its content in real time while the black envelope is being adjusted. Instantaneous updating the result panel is the default behaviour on all UNIX-based systems. If this function is invoked when a ✓ mark is to its left, the result panel will not update its content while the black envelope is being adjusted; its content will only be updated after the left mouse button is released. Updating the result panel after the left mouse button is released is the default behaviour on Microsoft Windows systems.

• The result panel:

  • The result panel always keeps what it displays in sync with the black envelope.

  • The current seed profile is drawn in the result panel if and only if it is within the black envelope.

  • All observation profiles are drawn in their original colors.

  • Its right-click menu supports the following operations:

    • Copy

    • Save as PNG Image...

    • Set Background...

  • The cursor in the result panel is , which means you can click on profiles to identify observations represented by those profiles.

• The Auto Paint button paints all observations [1] either blue or red. An observation is painted blue if it is within the black envelope; otherwise, it's painted red.

This operation does not select any seed profiles. It constructs an envelope that includes all observation profiles. You then proceed to adjust this envelope to trawl through the data for interesting profiles.

Use the data in Figure 9-13, which contains only blue observations [1], to illustrate this operation. The left panel of Figure 9-17 is a snapshot of the Find in Ranges dialog right after it was popped up; the right panel is a snapshot of the same dialog after the envelope was adjusted.

Figure 9-17. Find in Ranges dialogs

---> images/pcp-mode-find-in-ranges-initial.png <--- ---> images/pcp-mode-find-in-ranges-final.png <---

This operation draws a parallel coordinate plot in such a way that each axis uses a different scale so that the minimum and the maximum values of the variable at the axis are mapped to the bottom and the top of the available drawing room. Stretched parallel coordinate plots are good for detecting clusters visually. Figure 9-18 is a stretched parallel coordinate plot displaying the same data as Figure 9-13.

This draws a stretched parallel coordinate plot in grayscale where the brightness of a pixel encodes the number of observation profiles passing through it. This drawing technique can reveal the internal structure obscured by overstriking. The right panel of Figure 9-19 is the x-rayed version of Figure 9-18.

Figure 9-19. Displaying PCP's in grayscale

---> images/plot-pcp-x-rayed-example.png <--- ---> images/plot-pcp-stretched-x-rayed-example.png <---

This draws a parallel coordinate plot in grayscale where the brightness of a pixel encodes the number of observation profiles passing through it. This drawing technique can reveal the internal structure obscured by overstriking. The left panel of Figure 9-19 is the x-rayed version of Figure 9-13.

There are a few properties and operations specific to x-rayed parallel coordinate plots:

• When in mode, the pointed profiles will be highlighted in their original colors. For example, the following left panel is a PCP with observations of 3 colors; the right panel illustrates 4 profiles being identified by the hand cursor.

  ---> images/pcp-with-3-colors.png <--- ---> images/pcp-with-3-colors-x-rayed-identified.png <---

• Retrieve Data by Pointing... from the right-click menu of the mode also highlights pointed profiles in their original colors.

• Adjust Gamma... can make an x-rayed image brighter or darker.

• Animate Color Distribution... in the right-click menu can help you visually correlate high density areas in an x-rayed image with observations of a specified color.