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#### A.4.1.2 Axis Configuration and Zooming

In general terms the axes on which the graphics are plotted are defined by the datasets you have selected. The axis labels are set from the column names or expressions chosen for the Main dataset, and the ranges are determined so that all the data from the chosen datasets can be seen. However, these things can be adjusted manually.

The following features are available directly from the window for configuring axis range:

X-Y Zoom
  In some of the windows (2d scatter plot, histogram and density map), you can change both axis ranges by zooming in or out with the mouse on the plot surface itself. To zoom in, place the mouse at the top left of the region you want to examine, press the button, drag it to the bottom right corner, and release the button. To zoom out, drag up and left instead. A box is drawn as you drag so you can see what you're doing.
Centre Zoom
  The 3d and spherical plots allow you to zoom in on the central part of the window. The 'active region' for dragging is to the left or right of the plot (the region on the right is rather thin, and does not include the width used by the legend). When the pointer is in these regions, the mouse cursor symbol should change to indicate that zooming can be done. Drag down to zoom in and up to zoom out.

  An easier alternative for zooming in the 3D windows is to use the mouse wheel, if you have one: wheel forward to zoom in and backward to zoom out.

Axis Zoom
  In some of the windows (2d scatter plot, histogram, density map, stacked lines) you can modify the range on each axis independently by dragging the mouse over where the axis is drawn. The 'active region' for dragging is just below the X axis and just to the left of the Y axis, in the region where the numeric and text labels are written. When the pointer is in one of these regions, the mouse cursor symbol should change to indicate that zooming can be done. As for the X-Y Zoom, drag left-to-right or up-to-down to zoom in and right-to-left or down-to-up to zoom out.
Auxiliary (Colour) Axis Zoom
  When Auxilary Axes are in use, you can zoom in and out of them by dragging up and down on the colour bar to the right of the plot, in the same way as for a normal Axis Zoom above.
Rescale
  If you find you're zoomed to a region you don't want to be in, you can use the Rescale toolbar button to return to the default scale (full coverage). Note this affects any auxiliary axes as well as the spatial ones. Some windows may have per-axis rescale buttons too (, ).

For more control over axis range and labelling, use the Configure Axes and Title () toolbar button, which will pop up a dialogue like the following:

Axis Configuration Dialogue for 2-d axes

You can fill in these values for each axis as follows:

Label
  For each axis the label box contains the text used to annotate the axis in the plot. By default this is the same as the text in the Main dataset column selector (usually a column name), followed by the units if known. However, you can change it by typing whatever text you like.
Range
  The range boxes allow you to specify the lower and upper limits of each axis. By default these are blank, meaning that the plot will size its axes so that all the data can be seen. However, if you fill in one or both of the boxes with a suitable numeric value, the lower/upper bound will be fixed at that. Note that the lower bound (left box) must be numerically less than the upper bound (right box).

Both values are reset if the plot's axis is changed (a new column or expression is selected for the Main dataset), or if the range is reset in some other way (e.g. by zooming).

The plot title may also be set in the Plot Title panel of this window:

Title
  Any text entered here will be displayed at the top of the plot to provide a title.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk