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Standard deviation over a data set
Posted 01.11.2013, 02:05 GMT-4 Parameters, Variables, & Functions, Studies & Solvers Version 4.3b 1 Reply
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Hello Forum,
Is there an easier method to calculate the standard variation of a variable (e.g., flow velocity) over a predefined data set (e.g., a cut plane or a cut line) rather than importing the data to MATLAB? I can't find anything and I am surprised that COMSOL doesn't have such a basic capability!
Thanks for your input!
Hadi
Is there an easier method to calculate the standard variation of a variable (e.g., flow velocity) over a predefined data set (e.g., a cut plane or a cut line) rather than importing the data to MATLAB? I can't find anything and I am surprised that COMSOL doesn't have such a basic capability!
Thanks for your input!
Hadi
1 Reply Last Post 04.11.2013, 03:16 GMT-5
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Posted:
1 decade ago
Hello,
There is no predefined operation for computing the standard deviation over a data set, but you can do it in COMSOL using the following steps:
1. Compute the average of the expression ("expr") for which you want to compute the standard deviation using a Line Average feature (under Results>Derived Values).
2. Copy and paste the numerical average value ("av") into the expression "(expr-av)^2" in another (or the same) Line Average feature (replace "av" with the numerical value computed in Step 1).
3. Compute the square root of the value computed in Step 2.
If you can define the line or plane of interest directly in the geometry, you can evaluate the standard deviation for a selection of geometric entities (a line, for example), where you define an Average coupling operator (aveop1, for example). Then use the expression
sqrt(aveop1((expr-aveop1(expr))^2))
for the standard deviation. We are looking into providing more direct support for computing the standard deviation in future versions of COMSOL.
Best regards,
Magnus Ringh, COMSOL
There is no predefined operation for computing the standard deviation over a data set, but you can do it in COMSOL using the following steps:
1. Compute the average of the expression ("expr") for which you want to compute the standard deviation using a Line Average feature (under Results>Derived Values).
2. Copy and paste the numerical average value ("av") into the expression "(expr-av)^2" in another (or the same) Line Average feature (replace "av" with the numerical value computed in Step 1).
3. Compute the square root of the value computed in Step 2.
If you can define the line or plane of interest directly in the geometry, you can evaluate the standard deviation for a selection of geometric entities (a line, for example), where you define an Average coupling operator (aveop1, for example). Then use the expression
sqrt(aveop1((expr-aveop1(expr))^2))
for the standard deviation. We are looking into providing more direct support for computing the standard deviation in future versions of COMSOL.
Best regards,
Magnus Ringh, COMSOL