Mathematical mean functions

modelica / ModelicaStandardLibrary

Free (standard conforming) library to model mechanical (1D/3D), electrical (analog, digital, machines), magnetic, thermal, fluid, control systems and hierarchical state machines. Also numerical functions and functions for strings, files and streams are included.

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Mathematical mean functions #1400

Open modelica-trac-importer opened 7 years ago

modelica-trac-importer commented 7 years ago

Reported by kdavies on 17 Jan 2014 00:39 UTC This ticket is to add a package of mathematical mean functions to Modelica.Math. They were necessary for a model library I created and maybe they are useful to others.

Migrated-From: https://trac.modelica.org/Modelica/ticket/1400

modelica-trac-importer commented 7 years ago

Comment by hansolsson on 17 Jan 2014 09:20 UTC I think we need to consider these in more detail: first and foremost exactly what we need in MSL (do we need mean-functions at all? other similar functions? the median? as blocks as well?), and then where to place these functions.

Looking at the proposed implementation I see two issues:

No guard against unnecessary overflow. The product of all elements is likely to overflow for longer vectors (just think of a geometric mean of a vector of 100 values each between 50 and 100)- there are ways of handling that, but it makes the algorithm longer - especially if you want to avoid any unnecessary rounding errors as well.
Too many ifs. Having a special case for size=2 is not needed, and I found it more confusing for the harmonic mean.

modelica-trac-importer commented 7 years ago

Comment by Kevin Davies on 17 Jan 2014 15:56 UTC I understand. I was hesitant myself (re: if and where they should be included in MSL), but I thought I may as well share them. You can close this if you want. If you decide to take it, then I'll improve the implementation.

beutlich commented 7 years ago

@kdavies4 @HansOlsson Can this issue be closed now that there is Mean, RectifiedMean, ContinuousMean, RootMeanSquare, Variance and StandardDeviation in Modelica.Blocks.Math of MSL v3.2.2?

HansOlsson commented 7 years ago

I don't think we can close this just because there are blocks for Mean etc; since these functions could be used to perform analysis inside algorithms.