Classify by Code

Use the Geochem Analysis > Classify by Code option (CHLIMASK GX) to create or update a mask channel based on values matched from any other channel. 

Window Using Code dialog options

Channel	Any channel, text or numeric. Script Parameter: CHLIMASK.CHAN
Code	Number or text string to match. Script Parameter: CHLIMASK.CODE
Mask channel	Mask channel to create or append. The default mask channel is set from the CHPREFERENCES GX (Geochem Import/Preferences...). Script Parameter: CHLIMASK.MASK
Append/New	Select to append to a Mask channel or create new Mask channel. "Append" means that values that are already selected ("1") in the Mask channel will remain selected – these will not be reset to "dummy" even if the data is not found to be included in the current masking operation. "New" means that every value in the mask channel will be updated based on the current mask operation. Script Parameter: CHLIMASK.NEW

Application Notes

This GX was originally created for updating a mask channel based on a lithology channel, but it works equally well for any channel (even floating-point channels, where the number of decimals is small enough that they may reliably be converted to a text string which can be matched against).

For example, the channel might contain known codes such as:

grn = granite

ss = sandstone

Select the code channel, the code you wish to use for masking (grn), the mask channel (the default is "ChemMask"), and whether you wish to create a new mask channel or append to an existing one.

When classifying by lithology code, the objective is to use the known geology obtained from field books and create a subset database based on specific lithologic units of interest. For example, you may wish to select one or more lithology codes, for example sandstones (SS) and siltstones (SST), and subset based on these codes.

This method requires that you have a channel containing codes in your database. You can either import this channel directly with your field data as described in the import documentation or import your field data and add this information later. Codes are typically strings (i.e. character-based), but may also be integers (even floating point values will work, as long as they are displayed to their full precision).

Working with the ChemMask Channel

The Classify by code method assumes that you will subset to ChemMask channel, look at the results and the APPEND ChemMask with the next group. If you want to save a particular ChemMask combination, we recommend that you copy the ChemMask to another channel, BEFORE adding another group, since the process will automatically APPEND. You also have the option of creating a new masking channel with another name.