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Analytic function with multiple lower/upper limits
Posted 25 août 2015, 15:16 UTC−4 Heat Transfer & Phase Change, Materials, Parameters, Variables, & Functions, Structural Mechanics Version 4.4 2 Replies
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I'm trying to define an analytic function in the global definition that has multiple definitions over different range. For example, the expression is x, when 0<x<=20; the expression is 2x^2+1 when 20<x<=50, so on. How should I combine them into one analytic function? Or should I just define a bunch of them then somehow use all of them later (in the material properties for example)?
Any help is much appreciated! Thanks!
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Or in simple steps, for example:
1 - Define a new step centered around 20 that goes from 1 to 0. Call it step1.
2 - Define a new analytic function, call it an1. In the expression field write: step1(x)*x
You know have a function that is equal to x from 0 to 20.... And you could add in the expression field a second function that's zero everywhere except 20 to 50 and so on.
You probably want to use the built-in primitives (step, rectangle, etc.) but you can also go with logical functions ( eg (x <5) is another step function that goes from 1 to zero at 5 ). The problem is that these are not smooth so they could lead to trouble.
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I managed to use the Piecewise function to solve the problem. But I guess your suggestion also should work.