EXPRESSION EVALUATOR |

**Simple operators:**+ - * / ^ ( )**Complex operators:**EXP, LOG or LN, LOG10, SIN, COS, TAN, ATN or ATAN, ABS, INT, SQR (square), SQRT (square root)- Two
**special variables**(i.e.,**channels**) named**"**X**"**and**"**Y**"**, chosen with push-buttons (see image below) **PI**(or the equivalent Greek letter)**Numbers**(such as 5, -3.1889, and 1e-10)- You can add a comment at the end of your expression, delineated with the " ` " character.

Some general considerations:

- The '
**Check expression**' button does a preliminary parsing of the expression and indicates if there are any syntax errors (in the above example, this button has been clicked). - The '
**Evaluate**' button processes the X and Y values according to the expression in the upper left window. Results are shown in the yellow text box at the bottom of the window. If any errors are found (see below), a warming message is shown.

NOTE:This routine will only 'catch' errors in the basic numeric expression.such as division by zero, or taking the log or a non-integer exponent of a negative number. If such situations occur, results may be unpredictable. The algorithm does find most such errors during processing, however.It may not detect invalid or meaningless math operations that may be attempted when data are processed,

The underlying code for theexpression evaluatorwas developed by the late, greatRobert Purves(recently deceased and greatly missed). I 'borrowed' it -- with his permission -- and made some modifications forLabHelper. But Robert P. deserves all the credit.

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