Step 1: Build the Expression

You can enter a mathematical expression manually or construct it using the tabs and buttons below the Expression box.

• Enter the math expression using C-style syntax.

• The expression can contain any combination of functions and operators, absolute or variable channel names, DUMMY values, and numbers. Multiple equations are supported.

• You can type the expression or build it using the Variable & Operators and Functions tabs.

See the Expression section under Application Notes for more details.

Click the toggle to expand and view the available Operators and Functions. Use your keyboard to enter numerical values.

Click on the links below to explore the tools and available tabs:

• Common Keys: Frequently used operations and values, conveniently grouped just below the Operators and Functions section.

• Frequent Tab: Common conditional and logarithmic operators and functions.

• Special Tab: Specialized mathematical functions.

• String Tab: String functions. Only appears if string-type channels exist.

• Trig Tab: Trigonometric functions.

• Statistics Tab: Statistical properties calculated from one or more lines.

• Offset Tab: Operators to access channel values from non-current rows.

• Date Tab: Convert between Julian date (day, month, year) and Geodate (fractional years).

• Time Tab: Convert between standard time (second, minute, hour) and Geotime (fractional hours).

Click this button to insert a new channel variable at the location of the cursor into the Expression box. The variable channel naming convention is C#, where # is the next unused number.

Step 2: Assign Channels

Assign channels from the current database to the variable names used in the expression.

Populated automatically with all the channel variables present in the Expression box.

Select from the drop-down list the appropriate channel name to assign to each of the variables in the expression. The list is populated with the channel names from the current database.

The tool distinguishes between input and output channels:

• Input channels are preceded by a character and must be selected from the list.

• Output channels can be selected from the list of existing channels or created by typing a new name.

See the Assign Channels section in the Application Notes for more guidance.

Use the drop-down list to quickly insert commonly used expressions:

• Add 2 Channels: C0 = C1 + C2;

• Divide 2 channels: C0 = C1 / C2;

• Multiply 2 channels: C0 = C1 * C2;

• Multiply channel by factor 2: C0 = C1 * 2;

• Remove 5000 from channel: C0 = C1 - 5000;

• Subtract 2 channels: C0 = C1 - C2;

• True/False statement: C0 = (C1>5000) ? C2 :C3;

You may further modify selected expressions as needed.

Once you have built the expression, you can save it to a file for reuse. Similarly, if you have previously saved expressions, you can load them from a file.

The expression files are plain ASCII text and can be viewed outside Oasis montaj in a text editor.

Click Clear to remove all entries, including the expression, channel assignment, and any loaded expression file.

Click Apply to execute the expression without closing the dialog–useful for applying the same expression across multiple channels in the same database.