User-defined transforms

At the top of the Parameters dialog for transforms, choose user-defined X functions or user-defined Y functions. Select a user-defined transform you have used before or enter a new one.

You can write equations so different data sets get different transforms. Put <B> in front of a line in your transform that only applies to data set B. Put <~A> in front of a line that applies to all data sets except data set A.

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Transforms of X that include Y in the function -- If you are transforming X values, you may use Y in the function. If the data table contains several data sets (so has several Y values for a single X value), Prism will stagger the results down the page, repeating X values as needed. The results for column A will appear on top of the results table. Below that Prism will place the results for column B. For these rows, column A will be empty. You may use any of these functions when writing your equation.

Don't mix up the sqr() function, which squares the value, with the sqrt() function, which takes the square root.

•	If-then transforms -- Prism allows you to introduce some branching logic through use of the IF function. The syntax is:

You can precede a conditional expression with NOT, and can connect two conditional expressions with AND or OR. Examples of conditional expressions:

MAX>100
Ymax=Constraint
(A<B or A<C)
NOT(A<B AND A<C)
FRACTION<>1.0
X<=A and X>=B

Note: “<>” means not equal to, “<=” means less than or equal to, and “>=” means greater than or equal to.

If Y is less than Y0, then Y is unchanged. Otherwise Y is transformed to Y squared.

Here is a function that returns Y if Y is positive or zero, but otherwise leaves the results blank. In other words, it removes all negative values. The way to leave a result blank is to do an impossible mathematical transform such as dividing by zero.