Function call does not evaluate numerically inside a for() loop - Сообщения
#1 Опубликовано: 15.04.2018 03:23:52
Good day SMath community,
I was battling this issue in my worksheet for a better part of the weekend.
I wrote a formula (biaxial bending in a column) to calculate unknown input loads based on known response. A key to practical use of the formula is to solve for unknown response based on known input loads (backwards of what formula does). I attempted to use FindRoot() with no success.
I decided to write a simple "solver" using a for() loop, which i have done many other times before. To my surprise the custom formula does not evaluate correctly inside the for() loop, while evaulating just fine outside it.
This is rather baffling. Please take a look and help - i honestly dont know what to do here - this should be a simple task which proved to be very stubborn.
Many thanks!
I was battling this issue in my worksheet for a better part of the weekend.
I wrote a formula (biaxial bending in a column) to calculate unknown input loads based on known response. A key to practical use of the formula is to solve for unknown response based on known input loads (backwards of what formula does). I attempted to use FindRoot() with no success.
I decided to write a simple "solver" using a for() loop, which i have done many other times before. To my surprise the custom formula does not evaluate correctly inside the for() loop, while evaulating just fine outside it.
This is rather baffling. Please take a look and help - i honestly dont know what to do here - this should be a simple task which proved to be very stubborn.
Many thanks!
#2 Опубликовано: 15.04.2018 06:04:10
Hello Alex,
The loop fails on i=2, where the neutral axis has a value that doesn't cross the section; looking at biaxial(2) this case is not handled (local variable #chunk not defined -> error on stress block properties calculation -> error in the loop)
This is by design since SMath Studio 0.99.6622
I decided to write a simple "solver" using a for() loop, which i have done many other times before. To my surprise the custom formula does not evaluate correctly inside the for() loop, while evaulating just fine outside it.
The loop fails on i=2, where the neutral axis has a value that doesn't cross the section; looking at biaxial(2) this case is not handled (local variable #chunk not defined -> error on stress block properties calculation -> error in the loop)
definition of xii "erased"
This is by design since SMath Studio 0.99.6622
Calculation error happened during definition of the variable/function clears previous value of this variable/function if it is available;
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Alexander O. Melnik 15.04.2018 12:39:00
#3 Опубликовано: 15.04.2018 10:39:33
This is rather baffling. Please take a look and help - i honestly dont know what to do here - this should be a simple task which proved to be very stubborn.
Alex, everything is OK and NOT in few points.
I worked a bit on your previous version. Now the last error "_ not defined"
The incompatibility is too deep to be isolated... % appears as a factor is
no problem for FindRoot solver. rotation° is the problem in the solver.
The function is OK in the program data*rot(,), but the solver does not solve
for (°) because the demand is for solving the argument of a function of a function..
This in Mathcad is possible via an iterative Given/Find, not directly possible in Smath.
What you can do and in fact is what you need, create a matrix of solutions from
... biaxial(°,%) ... works fine in the attached 6179
Cheers Alex ... Jean
formula[1].sm
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Alexander O. Melnik 15.04.2018 12:39:00
#4 Опубликовано: 15.04.2018 12:38:32
Oh thank you very much Davide and Jean, now i have something to work with :-)
Jean, i entertained initially the idea of creating a matrix of solutions, but what proved to be a challenge is to interpolate the desired one from said matrix (which is a 3D surface)
Davide, so is "variable undefined" a sign that function evaluated to an error?
I managed to get my solution using a for() loop by removing the error you mentioned, but once i encapsulate said for loop in a function call the error is back
formulaR2.sm
Jean, i entertained initially the idea of creating a matrix of solutions, but what proved to be a challenge is to interpolate the desired one from said matrix (which is a 3D surface)
Davide, so is "variable undefined" a sign that function evaluated to an error?
I managed to get my solution using a for() loop by removing the error you mentioned, but once i encapsulate said for loop in a function call the error is back
formulaR2.sm
#5 Опубликовано: 15.04.2018 14:19:12
Oh thank you very much Davide and Jean, noiw i have something to work with :-)
Jean, i entertained initially the idea of creating a matrix of solutions, but what proved to be a challenge is to interpolate the desire one from said matrix (which is a 3D surface)
Alex,
Your "self entertaining" was correct, but unfortunately up to this point,
you have a system, not a surface. Mathcad would plot nothing either.
Most probably it would generate "a critical error occured".
The last olive can be programmed for convenience.
I love projects that understand nothing but work !
I'm not a bridge maker, just a Process Control old man.
Cheers Alex ... Jean
formula[2].sm
#6 Опубликовано: 15.04.2018 17:22:42
... Alex,
From this completed demo, you can:
interpolate [cinterp from sanity plots]
I tried some surface interpolation,
too small data set [4 x 3].
Jean
formula[3].sm
From this completed demo, you can:
interpolate [cinterp from sanity plots]
I tried some surface interpolation,
too small data set [4 x 3].
Jean
formula[3].sm
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Alexander O. Melnik 15.04.2018 18:33:00
#7 Опубликовано: 15.04.2018 18:36:16
... Alex,
From this completed demo, you can:
interpolate [cinterp from sanity plots]
I tried some surface interpolation,
too small data set [4 x 3].
Jean
formula[3].sm
Hi Jean, greatly appreciate your help. In the example you developed, can you interpolate unknown values of "°" & "%" based on given values of P.z and ratio Mx/My? or find all possible values Mx and My for a known value of Pz This is what i am after. Surface defined by dots in coordinate system (PzMxMy) is an interaction diagram of column failure
#8 Опубликовано: 15.04.2018 20:26:07
I have attempted to approach the task from a different angle - parametrically define Pz(a#,na#) Mx(a#,na#) My(a#,na#)
and solve for a# and na# by evaluating Pz, Mx, My using function at().
Function at() does not work with my definition.
Davide, why am i hitting a brick wall here?
ThanksBiaxialColumnCheck.sm
and solve for a# and na# by evaluating Pz, Mx, My using function at().
Function at() does not work with my definition.
Davide, why am i hitting a brick wall here?
ThanksBiaxialColumnCheck.sm
#9 Опубликовано: 15.04.2018 20:57:25
Hi Jean,
1. In the example you developed, can you interpolate
unknown values of "°" & "%" based on given values of Pz and ratio Mx/My?
2. or find all possible values Mx and My for a known value of Pz.
This is what I am after.
3. Surface defined by dots in coordinate system (PzMxMy)
is an interaction diagram of column failure
================================================
1. done, perfect
2. Don't understand completely
3. up until now, does not work well [NFG !]
1. In the example you developed, can you interpolate
unknown values of "°" & "%" based on given values of Pz and ratio Mx/My?
2. or find all possible values Mx and My for a known value of Pz.
This is what I am after.
3. Surface defined by dots in coordinate system (PzMxMy)
is an interaction diagram of column failure
================================================
1. done, perfect
2. Don't understand completely
3. up until now, does not work well [NFG !]
#10 Опубликовано: 15.04.2018 22:25:17
1. done, perfect
2. Don't understand completely
3. up until now, does not work well [NFG !]
================================
1 & 3 done
Can you re-explain your # 2
Alex3D.sm
formula[3] Copy.sm
The 3D crashes the main sheet
#11 Опубликовано: 15.04.2018 22:33:19
2. or find all possible values Mx and My for a known value of Pz.
This is what I am after.
=====================================
I think it's possible
This is what I am after.
=====================================
I think it's possible
#12 Опубликовано: 15.04.2018 22:40:35
1. done, perfect
2. Don't understand completely
3. up until now, does not work well [NFG !]
================================
1 & 3 done
Can you re-explain your # 2
Alex3D.sm
formula[3] Copy.sm
The 3D crashes the main sheet
Hi Jean, huge effort here from you - BIG thanks. Will take some time for me to digest. To make it a little easier for me can you point out where i can "interpolate unknown values of "°" & "%" based on given values of Pz and ratio Mx/My?". I know Pz, ratio of Mx/Mz and need to find "°" & "%" that correspond to it (all data is spit out by biaxial() formula).
Many Thanks!
#13 Опубликовано: 15.04.2018 23:29:52
Hi Jean, huge effort here from you - BIG thanks. Will take some time for me to digest. To make it a little easier for me can you point out where i can "interpolate unknown values of "°"
====== will be back on that tomorrow ======
Here is the lookup wrt PzMxMy, alternately search from either col.
formula[3] Copy.sm
#14 Опубликовано: 16.04.2018 01:01:37
To make it a little easier for me can you point out where
I can "interpolate unknown values of "°"
Maybe, I didn't completely understood ?
Here is the refreshed version.
formula[3] Copy.sm
#15 Опубликовано: 16.04.2018 04:32:52
I managed to get my solution using a for() loop by removing the error you mentioned, but once i encapsulate said for loop in a function call the error is back
The problem here is that when you pass to a function an argument that requires numerical evalution and the evaluation is not possible because undefined variables, the preprocessing fails (at smath level)
the workaround is to create a function that internally defines the leftside as the function that cannot be passed in argument and call your solver internally
notice eval@ inside the solver, this makes possible to use solveNR both directly (with at()) both within the wrapper function solvePcr (not sure now why at() doesn't work in both the cases, have to investigate when it will be possible)
formulaR2_rev2.sm
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frapuano 16.04.2018 07:52:00
#16 Опубликовано: 16.04.2018 10:57:04
Davide, Alex ... thanks for the distiller-solution.
Two points about your Newton-Raphson example:
1. Will it work for this application in traditional code ?
2. Two [2] pitfalls:
2\a. about your cubic, it is ill-posed. In maths, it is paramount
polynomials are expressed in Lagrange canonical format.
For quick getting the polyroots and set the cubic solver.
In fact, cubic may have complex roots [your example is cubic complex].
Complex solutions are essentials in modeling/solving Control Systems.
2\b. The Smath native "roots" solves directly your example.
Rev(2) most appreciated for eventual hard solving future.
Solve roots Newton-Raphson.sm
Two points about your Newton-Raphson example:
1. Will it work for this application in traditional code ?
2. Two [2] pitfalls:
2\a. about your cubic, it is ill-posed. In maths, it is paramount
polynomials are expressed in Lagrange canonical format.
For quick getting the polyroots and set the cubic solver.
In fact, cubic may have complex roots [your example is cubic complex].
Complex solutions are essentials in modeling/solving Control Systems.
2\b. The Smath native "roots" solves directly your example.
Rev(2) most appreciated for eventual hard solving future.
Solve roots Newton-Raphson.sm
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Alexander O. Melnik 17.04.2018 01:05:00
#17 Опубликовано: 17.04.2018 13:21:34
investigated a few options:
1. point interpolation on a surface is tough to implement (for me)
2. Solving for na# works well (Davide's last post)
3. Solving for rotation does not work well (relationship is far from linear, solver chokes up too often - see example formulaR4.sm )
My current solution is solve for na# (Davide's last post) by bracketing the rotation till desired Mx/My is achieved (not shown here)
1. point interpolation on a surface is tough to implement (for me)
2. Solving for na# works well (Davide's last post)
3. Solving for rotation does not work well (relationship is far from linear, solver chokes up too often - see example formulaR4.sm )
My current solution is solve for na# (Davide's last post) by bracketing the rotation till desired Mx/My is achieved (not shown here)
#18 Опубликовано: 17.04.2018 14:40:12
investigated a few options:
1. point interpolation on a surface is tough to implement (for me)
2. Solving for na# works well (Davide's last post)
3. Solving for rotation does not work well (relationship is far from linear, solver chokes up too often - see example Project_0 Biaxial SolveRotdeg.sm
#19 Опубликовано: 17.04.2018 18:34:16
... suite,
by solving, simultaneously [rot°, _%], if biaxial would be an analytical f(x,y)
you can solve x<=y or vice versa y<=x. Up until now, found only one that Smath/Maple
does not solve. On the other hand, biaxial(rot°, _%) generates 3 sets of results.
The CreateMesh [not the Smath CreateMesh] can alternately scan/evaluate and tabulate
results for further use ... I'm working on that, in the mean time, if you have a good
range of each [rot°, _%] that would be nice, though easy to modify.
by solving, simultaneously [rot°, _%], if biaxial would be an analytical f(x,y)
you can solve x<=y or vice versa y<=x. Up until now, found only one that Smath/Maple
does not solve. On the other hand, biaxial(rot°, _%) generates 3 sets of results.
The CreateMesh [not the Smath CreateMesh] can alternately scan/evaluate and tabulate
results for further use ... I'm working on that, in the mean time, if you have a good
range of each [rot°, _%] that would be nice, though easy to modify.
#20 Опубликовано: 18.04.2018 00:31:56
... suite as far as manageable.
I got lost in your last attempt !
Cheers Alex
Project_0 Biaxial SolveRotdeg.sm
I got lost in your last attempt !
Cheers Alex
Project_0 Biaxial SolveRotdeg.sm
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