This page covers:

• What is a graph variable?
• How to edit graphs
• How graph variables function on a technical level

What is a graph variable?

It's one of these!

A graph variable is a setting that changes based on some other factor, such as Brightness by velocity. This means the output brightness changes based on the incoming velocity, allowing dynamic response and deeper visualisation.

Sometimes it can be a little difficult to spot graph variables, as any graph variable can operate as a flat slider where it only outputs a static value regardless of the input factor and thus does not visually look like a graph. Many settings are set to be flat values by default, obscuring the fact that they can operate in graph mode. Any variable title with these icons in the top right corner can operate in either flat or graph mode:

How to edit graphs

The first step to editing a graph variable is deciding whether you want a flat or graph value using the mode icons in the top right.

Dragging

When using graph mode, the handles can be click-and-dragged to adjust both Start / Min and Stop / Max values at the same time.

Alt modifier (smooth dragging)

While dragging, holding the Alt key will disable value snapping while held. This can be useful for fine adjustment or getting values very close together. This modifier key also works on flat value sliders not capable of graph mode.

Shift modifier (proportional editing)

While dragging, holding the Shift key will proportionally edit the other handle, snapped to the opposing corner (so, Shift-dragging right handle will "pin" the graph to the bottom left corner). This can be useful for keeping the same ratio of response in a variable while changing its amplitude.

Ctrl modifier (graph panning)

While dragging, holding the Ctrl key will translate the graph inside the bounds. This is rarely useful, but is included here for completeness.

Editing values directly

All values can also be edited directly by simply typing in a number. This will also automatically adjust graph bounds (if possible) to fit the new value.

Graph bounds

Many variables can be set to values far outside of the typical graph bounds. When available, this is indicated by the small - + buttons next to the Y-axis bounds.

Graph bounds can be edited directly by typing in a number, or indirectly by simply entering a number for Min / Max that is outside the current graph range. When graph bounds are increased to have a range greater than the original range, snapping increments are also increased.

Copy / paste / reset

The small icon in the upper right corner can be used to reset the graph if necessary. Some default values on some variables may not be suitable for all presets though, so do not assume the default value is necessarily the best one.

By clicking on the title of a variable (both graph or flat value slider) and then pressing Ctrl+C, the variable can be copied. Hovering over another graph or slider and pressing Ctrl+V will paste the copied value (if possible).

How graph variables function

The following is a technical breakdown of how values are actually produced. This is somewhat obvious from the visual graph, so this section is optional extra reading.

How a value is output

Graph variables have eight internal values:

Mode      |   "Flat" or "Graph"
          |
Start     |  0.00 to 1.00 X-axis position of left handle
Stop      |  0.00 to 1.00 X-axis position of right handle
          |
Min       |  Y-axis value of left handle
Max       |  Y-axis value of right handle
          |
Curve     |  -1.0 to 1.0, used to generate graph curvature
          |
GraphMin  |  Graph region Y-axis lower bound (only relevant to UI)
GraphMax  |  Graph region Y-axis upper bound (only relevant to UI)

When a graph variable is used in Keysight, the very first thing it does is check whether the graph variable is in graph or flat Mode. If it is in flat Mode, the Max value is output immediately.

If it is in graph Mode, the variable is then provided with an input factor between 0.00 - 1.00. The graph is then sampled at the given input factor location, and outputs a final value somewhere between Min and Max.

How clamping and curvature works

Any incoming input factors below Start will be clamped to the Min value, and any above Stop will be clamped to the Max value.

The space between Start and Stop is where the Curve value is used.

• At 0.00 as shown above, the intervening space is a straight line (linear interpolation)
• At -1.00, value is "slow in, fast out" and traces a quarter circle
• At 1.00, value is "fast in, slow out" and traces a quarter circle
• Intervening values linearly interpolate between lines traced by 0.00 and +/-1.00