Derived Parameters

FlowJo allows you to add new parameters to your data. These parameters are not actually added to the original data files; they are simply descriptions of new parameters that are stored with the workspace. However, they behave in other regards like parameters that were collected: you can display them, calculate statistics on them, etc.

Because they are not stored with the data file, they will not appear if you open the same sample in a different workspace--you will have to add the derived parameters again in that workspace. Currently, there is no way to copy derived parameter definitions between workspaces.

There are six derived parameter types that you can create: Ratio, Time, Log->Linear, Linear->Log, Calibrated and Sum. This tool also will apply a Gain or Offset to an existing parameter.

To add a derived parameter, select the sample in the workspace, and then select the Derived Parameters... menu item from the Tools menu. You will be presented with a dialog tool that allows you to select and define new parameters. From this window, you can also remove existing derived parameters. For detailed help with creating a derived parameter, click here.

You can add a Ratio Parameter: this is the ratio of any two collected parameters. This is commonly necessary for calcium flux experiments, in which the ratio of Indo-1 fluorescence in two different channels is related to the calcium concentration. You can choose to create a ratio parameter with either linear or logarithmic scaling.

You can convert any collected parameter between log and linear. FlowJo will automatically optimize the scaling of the converted parameter to show the maximum number of events.

You can create a calibrated parameter. You can convert the scaling of any parameter to, for instance, absolute number of molecules per cell. While the Calibration tool creates a derived parameter automatically, you may wish to apply such a calibration to other samples. Do this by selecting the target population in the Workspace. Available parameter calibrations (created with the Calibration Tool) are listed under the Tools menu. Select one.

A light blue bar will appear in the Workspace next to the calibrated tubes.

The calibrated parameter name will appear in the graph of such tubes, in the axis label drop-down menu.

Finally, you can create a parameter that is the sum of the value of two parameters. Select a tube in the Workspace, select the DerivedParameters... menu item from the Tools menu, then, at the bottom of the Derived Parameters dialog, select two parameters from the drop-down list and click Add Sum Parameter.