Function with two different slopes and a drop.

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Hello, I'm trying to make a function that i can use in my pde.

Essentially i have two linear ramp functions that I want to be one,

(1) Baseline: 549054 Cutoff: 122170 Slope: -1452

(2) Baseline: 96570 Slope: -230 Cutoff: 0 it would look something like the attached image.

How can I go about this? help appreciated



2 Replies Last Post Jun 3, 2024, 2:26 a.m. EDT
Robert Koslover Certified Consultant

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Posted: 5 months ago May 31, 2024, 10:24 a.m. EDT
Updated: 5 months ago May 31, 2024, 10:27 a.m. EDT

Seems to me you could simply piece three linear functions together, using Booleans. That is, (1)write linear functions for each of the three segments, and then (2) where they join, use Boolean expressions. E.g., suppose ya(x) = the first function, yb(x) = the second function, and yc(x) = the third function. Suppose x1=x at the first junction and x2= x at the second junction. Your composite function is then: . The Boolean expressions resolve to 1 if true and 0 if false,so that each of your three functions contributes to ytot only over its appropriate domain.

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Seems to me you could simply piece three linear functions together, using Booleans. That is, (1)write linear functions for each of the three segments, and then (2) where they join, use Boolean expressions. E.g., suppose ya(x) = the first function, yb(x) = the second function, and yc(x) = the third function. Suppose x1=x at the first junction and x2= x at the second junction. Your composite function is then: ytot = ya*(x

Gunnar Andersson COMSOL Employee

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Posted: 5 months ago Jun 3, 2024, 2:26 a.m. EDT

The Piecewise function type can be used to stitch together the three linear functions without using Boolean expressions.

The Piecewise function type can be used to stitch together the three linear functions without using Boolean expressions.

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