In DAQFactory you are not limited to value vs. time trend graphs. You can plot just about anything vs. anything else. Doing so is as simple as providing both a Y and X expression for the trace. Either can be a simple channel name, or a complex calculation. When both expressions evaluate to a value with time associated with it, DAQFactory will automatically align the Y data to the X data's time. In this way you can easily generate XY graphs on data taken at different time scales. If you wish to turn off alignment, set the Align Threshold to a negative number. The Align Threshold only applies to the bottom axis.
Here are some things to think about when creating XY graphs
· If your data is randomly distributed in X then you will probably want to use the point plotting method, otherwise you will get a spaghetti of lines.
· If you provide a blank X expression for a trace, then the point number of the Y expression will be used for the X values.
· Even though there is only one X axis, each trace in your graph can have a completely different X expression. This is true on time graphs too.
· Because the Traces property tab uses the Y Expression to select which trace to edit, you must make sure each Y Expression is different. If you need to have the same Y Expression for multiple traces, presumably with different X Expressions, add something to make the expression different without changing the result. This can easily be done by adding an additional parenthesis pair, or doing +0, or something similar.
· Axis annotations only work if the X axis is displaying time, since they use the time of the data points to determine the flag location (though there are some ways around this using the InsertTime function).
· Markers don't work terribly well in XY graphs when the X data is randomly distributed. Sometimes when you move the markers with the keyboard, the markers can jump around unexpectedly. Since the graphs may be displaying constantly changing data, it is sometimes hard for the markers to get a lock on a data point.
· When using markers for ranging functions, especially Make NaN, remember that the range is determined by the X value of the two markers, not the data point number, but when making each point a NaN, it scans by data point number. Make NaN may work a little weird because of this, since it will start at the first point and scan through the data by point number until it finds a data point out of range.
