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Where is the maximum (or minimum)?

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Hello.

Does anyone know how to find (not only represent) the coordinates of the max (min) value of a variable, for instance in 3D? I mean, when one plots 'Max/Min Volume' (in a 3D Plot Group / More Plots), the maximum and minimum values of the chosen variable are shown graphically as points, but how to know their cartesian coordinates?

Thanks.

Jesus.

5 Replies Last Post 16 sept. 2016, 09:44 UTC−4
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Hello Jesus Lucio

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Posted: 1 decade ago 6 nov. 2012, 10:11 UTC−5
If you know where the maximum or minimum is, you can click on it and the coordinates and its value will show up in the Results tab (usually below the Graphics window). To get a more precise location, zoom in and click.

Another way, again if you have some idea of where the max or min is, is to draw a cut line or point (right-click on Data Sets under Results), and then plot it (right-click on Results, select 1D Plot Group, and then for a cut line, Line Graph).

It can be very helpful to narrow the search by establishing a Selection of a domain (right-click Data Sets under Results, to add a Solution, then right-click on the Solution to add a Selection, then select your domain).
If you know where the maximum or minimum is, you can click on it and the coordinates and its value will show up in the Results tab (usually below the Graphics window). To get a more precise location, zoom in and click. Another way, again if you have some idea of where the max or min is, is to draw a cut line or point (right-click on Data Sets under Results), and then plot it (right-click on Results, select 1D Plot Group, and then for a cut line, Line Graph). It can be very helpful to narrow the search by establishing a Selection of a domain (right-click Data Sets under Results, to add a Solution, then right-click on the Solution to add a Selection, then select your domain).

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 6 nov. 2012, 17:32 UTC−5
Hi

check the forum and your doc, the min and max operators can take a 2nd coordinate ,x,y,z or r and then will give outthe location of the maximum, respectively the minimum, you need to call it 3 times for 3D and it takes some time

--
Good luck
Ivar
Hi check the forum and your doc, the min and max operators can take a 2nd coordinate ,x,y,z or r and then will give outthe location of the maximum, respectively the minimum, you need to call it 3 times for 3D and it takes some time -- Good luck Ivar

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Posted: 1 decade ago 9 nov. 2012, 17:24 UTC−5
Hi Ivar,

I read the trail that I think you're referring to. But here's an easier way from Tech Support. Previously I've used Mathematica to find max or min in an exported file, which is fine. But I'd rather just look in COMSOL and figured there must be a way if they have a Max and Min function.

Kris

To find the coordinate of the location of the minimum and maximum of a
particular expression in a model you will need to add (to the appropriate
plot group) a Max/Min Volume (for 3D models or data sets), Max/Min Surface
(for 2D models or data sets), or Min/Max Line (for 1D models or data sets)
plot. When you right-click a plot group, these plot types can be found
using the "More Plots >" menu. Just type in the expression of interest and
when you click plot you will see points in the Graphics window labeling
where the min and max points are along with the associated min and max
values; also you will see the exact coordinates of these two points in a
table in the Results window (below the Graphics window) along with their
associated expression values.

For more information on this plot type, see pp. 487-488 in the COMSOL
Multiphysics Reference Guide. Documentation can be accessed within the
software via Help > Documentation or you can open this guide via the link I
created below:
Hi Ivar, I read the trail that I think you're referring to. But here's an easier way from Tech Support. Previously I've used Mathematica to find max or min in an exported file, which is fine. But I'd rather just look in COMSOL and figured there must be a way if they have a Max and Min function. Kris To find the coordinate of the location of the minimum and maximum of a particular expression in a model you will need to add (to the appropriate plot group) a Max/Min Volume (for 3D models or data sets), Max/Min Surface (for 2D models or data sets), or Min/Max Line (for 1D models or data sets) plot. When you right-click a plot group, these plot types can be found using the "More Plots >" menu. Just type in the expression of interest and when you click plot you will see points in the Graphics window labeling where the min and max points are along with the associated min and max values; also you will see the exact coordinates of these two points in a table in the Results window (below the Graphics window) along with their associated expression values. For more information on this plot type, see pp. 487-488 in the COMSOL Multiphysics Reference Guide. Documentation can be accessed within the software via Help > Documentation or you can open this guide via the link I created below:

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 10 nov. 2012, 04:12 UTC−5
Hi Kriss

I agree if it's to set some min max points on the graphs images, you have the plot options,

but if you need to retrieve the coordinates during solving or for further processing, you would need to use the operators min(,) or max with 2 arguments, but these are heavy computationally. Data set in max exist perhaps, will have to recheck once back in the office

--
Good luck
Ivar
Hi Kriss I agree if it's to set some min max points on the graphs images, you have the plot options, but if you need to retrieve the coordinates during solving or for further processing, you would need to use the operators min(,) or max with 2 arguments, but these are heavy computationally. Data set in max exist perhaps, will have to recheck once back in the office -- Good luck Ivar

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Posted: 8 years ago 16 sept. 2016, 09:44 UTC−4
Hi Guys,

do you know how I can call the max point?
I need to call ymax-y at each point of the soil profile to calculate the weigth over it.
no Idea how to intruduce ymax to the system.

bests
Hi Guys, do you know how I can call the max point? I need to call ymax-y at each point of the soil profile to calculate the weigth over it. no Idea how to intruduce ymax to the system. bests

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