TOPCAT Plane Plot Basics

Plane Plot Definition

• TOPCAT (Tool for Operations on Catalogues and Tables) uses plane plots as scatter plots
• Plane plots display position data points according to X and Y coordinates
• The plane plot is the most basic plot type in TOPCAT
• It is commonly used for two-dimensional graphs, and to visualize relationships between two variables or attributes in a dataset

Plot "Forms"

• Plot "forms" are instructions for shaping data representations on a plot.
• They use positional data from a table to determine shapes.
• "Mark" is the most common form, placing a marker at each data position.
• Each marker in the "Mark" form has a fixed shape and size.

1. Mark Form

• The 'Mark' form plots markers with a fixed shape and size.

1.1 Shading Mode

• Defines the basic color used for plotting each data point.
• Many forms allow selecting a shading mode to control the point's color.
• Shaded colors are based on the chosen style color
  • Shading influenced by the number of points at a location
  • Additional data coordinates
  • Other configuration details

1.1.1 Flat Mode

• The Flat shading mode colors points by the selected color style.
• It has no additional parameters.

1.1.2 Translucent Mode

• The Translucent mode uses a transparent version of the selected color style.
• Transparency depends on
  • Number of overlapping points.
  • Transparency Level slider settings.
• Increasing the slider to the right increases transparency.

1.1.3 Transparent Shading Mode

• Transparent shading mode applies a transparent version of the selected color style to shapes.
• Transparency controlled by the Opaque Limit slider.
• Moving the slider left makes points wholly opaque (like Flat mode).
• High opaque limit demands more overlapping points to achieve fully opaque color.
• Transparency is fixed by the opaque limit, and doesn't depend on point density.

1.1.4 Auto Shading Mode

• Auto shading mode colors isolated points in their chosen colors.
• Overlapping points darken to indicate density.
• Similar to Flat mode for isolated points, or points in non-crowded areas.
• Auto mode helps easily find dense areas in a plot.

1.1.5 Density Mode

• In TOPCAT Density mode shows crowded / dense regions of a plot using color variations.
• The colors reflect point overlap; more overlap = darker color.

1.1.5.1 Density Shader

• TOPCAT's Density Shader lets you pick a color style to display data density.
• Relative Maps adjust the base color based on density levels. This preserves original dataset colors.
  • Useful for comparing multiple datasets.
• Absolute Maps ignore original colors and make density stand out.
  • Beneficial for single datasets to highlight density.

1.1.5.2 Shader Flip

• Controls if the density scale maps forward or backward through the color map.

1.1.5.3 Shader Quantise

• TOPCAT allows adjusting the number of colors used in a color map (Shader Quantise).
• Fewer colors are visible as the value is increased. Instead of a smooth gradient, there are stepped layers of color.

1.1.5.4 Density Subrange

• Density Subrange lets you adjust the plotted density range.
• By default, all density values are covered.
• The slider lets you limit the range, focusing on selected density levels. This can highlight specific density areas

1.1.6 Aux Mode

• Aux mode shades each point based on an additional data coordinate value.
• The shading uses the overall color map; values represented by the shade.

1.1.6.1 Aux

• The aux coordinate is specified by name or a formula from the dataset table.

1.1.6.2 Opaque Limit

• Controls point transparency.
• Slider defaults to fully opaque points, moving it right gradually makes points more transparent

1.1.7 Weighted Mode

• TOPCAT Weighted mode uses colors based on point density.
• A weighting value assigned to each point affects the color intensity of each point.
• This mode lets you customize how these weights are combined to color each point.

1.2 Size Form

• The Size form adds data to a plot by adjusting the size of plot markers based on data values.

1.3 SizeXY Form

• The SizeXY form uses marker width / height values as data, independently, to reflect data, thus showing extra dimensions.

1.4 Vector Form

• Vector form plots directional lines from data positions, with delta values indicating changes in coordinates.

1.4.1 X Delta, Y Delta...

• These values, X Delta, Y Delta, etc, define the delta shifts applied at each point to create vector directions

1.4.2 Arrow

• Arrows are a selectable plotting marker style option.

1.4 XY Error

• X/Y Error markings display plotting errors in horizontal and vertical directions from column names/expressions.

1.5 Line Form

• Line form directly plots point-to-point lines across all the point data.

1.6 Linear Fit

• Linear Fit provides a straight line on a plot to identify general data trends.

1.7 Quantile Form

• Quantile form draws a line to show a specific percentage of values in a data range, ignoring extreme values.
• Line smoothing options provide clearer pattern identification.

1.6.1 Quantiles

• Quantiles define the range of values that should be visualized in each pixel, ranging from their minimum to maximum values, with 0.5 indicating the median

1.7 Label Form

• Labels identify points by each plot position value by displaying a text label.

1.8 Contour Form

• Contour form creates density plots.
• It offers an alternative approach to displaying over-dense regions in a crowded plot, along with other shading methods.

1.8.1 Levels

• Contour levels represent the specific values that contours in the plot are calculated from; these levels may contain no direct physical significance if combined with various combination values

1.9 Fill Form

• Fill form populates the plot region where values exist for a curve in a continuous way using a solid color .

1.10 Grid Form

• The Grid form displays 2D point data on a plot, dividing it into rectangular grid cells.
• Weighted values/ density maps, or 2D histograms can be shown.