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Automatic detection

To automatically add points on a curve:

To automatically add points on a dotted curve, a dashed horizontal curve, if the curve intersects other lines, or if the curve is too jittery:

Learn more about when to use a mask

To automatically add points on vertical or horizontal bar charts:

To automatically add points on symbols:

To automatically add points on the perimeter of an area:

Decting bars vs. symbols

Bar detection (which find regions of similar color) is much faster than symbol detection (based on pattern matching). Therefore, if symbols can be uniquely identified by their color, it is worth trying first the bar detection, since this option may actually detect correclty the symbols you want to digitize.

Adjust the detection parameters

The following parameters can be modified during the automatic detection:

Tolerance

GraphClick decides if a certain pixel of the graph belongs to a line base on the comparison of its color with the color of the pixel you clicked onto. A tolerance of 0% means that the colors must match exactly. Try to increase or to decrease the tolerance if not all points of the curve at detected.

Spacing

Indicates the spacing between points that are automatically detected.

Number of points

When detecting a horizontal curve, select this option and enter the number of points you want to detect. The detected points are equally spaced, the limits being either the border of the detected curve, or, if a mask is being used, the left and right sides of the mask region.

Note that the values of the above parameters, as well as the maximum number of points that may be automatically detected, can be changed from the GraphClick > Preferences (⌘,) window (under Detection).

Horizontal Offset

When detecting a horizontal curve, change this value to shift all points horizontally along the curve.

Start at extremity

When detecting a curve, use these options to indicate that the curve should be digitized from one of its extremity, instead of from the selected position.

Positions

When detecting bars, you can chose the positions where to add points for each detected bar. For instance: