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Calculating a New Variable

Engineers using Tecplot 360 or Tecplot Focus often need to create a new variable which is based on a numeric relationship of existing variables already loaded into Tecplot. This powerful capability for calculating a new variable uses this simple method:

In Tecplot 360 (or Focus) click on “Data” on the top menu bar, then click “Alter >> Specify Equations” which brings up this menu:
Calculating a New Variable
As an example, we will calculate the difference between two variables.

First select All Zones, and then type in the Equation(s) box to initialize the new variable QDifference:

{QDifference} = 0

Click on the “Compute” button

Next we will find the difference for variable Q between zone 2 and 3 (i.e. Q in zone 3 – Q in zone 2) to QDifference:

Select the zones you want to receive the difference value (you could put it in both zones 2 and 3 if you like) and type the following equation:

{QDifference} = {Q}[3] – {Q}[2]

Click on the “Compute” button

The new variable QDifference is now available for plotting.

You can learn more about calculating variables using the “Specify Equations” menu in Chapters 20 and 21 of the Tecplot 360 User Manual.

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