Set Mask Based on Data Range
Use the Set Mask Based on Data Range dialog (CHMASKRANGE GX) to set the mask channel based on values in a specified channel being within a specified range. The tool is accessed from the Apply Current Limits to Mask Channel button in the interactive tool Probability Analysis.
Set Mask Based on Data Range dialog options
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Mask channel
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Select a mask channel from the dropdown list. If the use of the mask channel is enabled, and set to this channel, only those data values whose corresponding mask channel value is not a dummy will be plotted or exported.
Channels must have their CLASS attribute set to MASK to appear as selections in the drop-down list. If the mask channel does not exist, it will be created with its CLASS attribute set to MASK.
The default mask channel is set from the CHPREFERENCES GX (Geochem Import/Preferences...).
Script Parameter: CHMASKRANGE.MASK
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Data channel
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Data channel to use. The mask channel is set depending on whether individual values in this channel fall inside or outside the defined range.
Script Parameter: CHMASKRANGE.CHAN
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Minimum Value
Maximum Value
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The end values of the range to consider. Whether these values are inclusive (and are considered the last values in the range) or exclusive (and are considered the first values not in the range) is determined by the "Minimum type" and "Maximum type" parameters.
Script Parameter: CHMASKRANGE.MIN, CHMASKRANGE.MASK
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Mask
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"Inside": The values inside the range will be masked out; in other words, only those rows of data where the value in the data channel lies outside the range will be used.
"Outside". The values outside the range will be masked out; in other words, only those rows of data where the value in the data channel lies outside the range will be used.
Script Parameter: CHMASKRANGE.INSIDE
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Minimum type
Maximum type
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"Inclusive" or "Exclusive". Inclusive means the value is considered part of the range, while Exclusive means that the value is not considered part of the range, and is in fact the first value outside the range. For instance, if the range 4-8 has an inclusive minimum and an exclusive maximum, then only values of x greater than or equal to 4, and less than 8 are considered part of the range. See the Application Notes below for a discussion of which type to use for different situations.
Script Parameter: CHMASKRANGE.INCMIN, CHMASKRANGE.INCMAX
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Application Notes
Inclusive and Exclusive Minima and Maxima
The decision of whether to use inclusive or exclusive minima and maxima depends on the application. Histograms ranges are defined with inclusive minima and exclusive maxima. For instance, if the histogram bin width is 2, then the following histogram ranges, starting from zero would be defined:
Bin # 1: 0 <= x < 2
Bin #2: 2 <= x < 4
Bin #3: 4 <= x < 6
etc.
These parameters are automatically set when plotting a range of data from the histogram tool.
Note, however, that Geosoft colour zones and ITR files are defined in the opposite manner; with exclusive minima and inclusive maxima. For instance, a colour zone file with increments of two would be defined as follows:
Zone #1: x <= 0
Zone #2: 0 < x <= 2
Zone #3: 2 < x <= 4
etc.
Last Zone: x > max defined zone value.
The two schemes are incompatible when considering discrete data and integral bounds. When applying colour zones to histogram bins for discrete (integral) data, you should be careful to define the zone bounds to be non-integers, for instance 0.5, 2.5, 4.5, etc.
