| Author | Message | |||
     Alex Klimenko (scorpion) New member Username: scorpion Post Number: 1 Registered: 03-2007 |
Dear Robert, please explain is there any possibility in FlexPDE to plot a time-dependent scalar function as a function of time? For example I have command report(bintegral(normal(grad(C)),"kathode")) as "Tok " Can I make a plot Tok(t)? Can I report somehow a maximum value of Tok? I mean Tok is a function of t but I need to know its maximum value. Thank you. | |||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 799 Registered: 06-2003 |
1. A HISTORY plot displays the time history of its argument. You want the following: PLOTS HISTORY(bintegral(normal(grad(C)),"kathode")) Or you can define TOK in the DEFINITIONS section and plot HISTORY(TOK). 2. To remember a temporal maximum, you'll have to use a GLOBAL VARIABLE (SCALAR VARIABLE in versions before 5): GLOBAL VARIABLES TokMax ... EQUATIONS ... TokMax = MAX(TokMax,TOK) | |||
| Alex Klimenko (scorpion) New member Username: scorpion Post Number: 2 Registered: 03-2007 |
Dear Robert, Ok, item 1 works fine but I have a problem with item 2. If TokMax were predefined then TokMax = MAX(TokMax,TOK) would be calculated correctly. But TokMax is a function of variable. Please look what I mean: PotokMax = MAX(PotokMax,bintegral(vx,"left border")) where vx is a variable. Without this simple equation everything is Ok. But with it I receive error message. If I use istead of vx something stricktly defined like 0,1, Sin(x) or even other variable p (which is prescribed on left border in BC) everything is OK. Is it possible to find a maximum of a function that depends on a variable? Thank you. Also is it possible to find a local maximum of the same construction? It looks like a beating sinusoid.
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| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 810 Registered: 06-2003 |
My earlier suggestion (Using a GLOBAL VARIABLE) turns out to be inadequate for a couple of reasons: 1) A Max function is not analytic, so it confuses Newton's method. 2) the bintegral is not updated on every Newton iteration unless you SELECT NRUPFIT. But if you do, the Max reports the max of all Newton trials, not of the final solutions. Anyway, what you wanted was a temporal maximum, so I have implemented two new functions, TIME_MIN(expr) and TIME_MAX(expr) to do this. The windows 32-bit version of this development release is in www.pdesolutions.com/download/xfpde5016x4win.exe This is a self-extracting archive containing only flexpde5.exe. It is not a full install. Extract the file over your old executable, or change the name of the old file first. This version will be released at some later time, perhaps with more updates, as version 5.0.16. So now you don't need a GLOBAL variable. Just define TokMax = TIME_MAX(TOK) in the definitions section. | |||
| Alex Klimenko (scorpion) Junior Member Username: scorpion Post Number: 3 Registered: 03-2007 |
Dear Robert, the link doesn't work. May be you've meant www.pdesolutions.com/download/xfpde1016x4win.exe Thank you for help very much | |||
| Alex Klimenko (scorpion) Member Username: scorpion Post Number: 4 Registered: 03-2007 |
OK, it works, thanks. | |||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 811 Registered: 06-2003 |
I made a typo when I posted it. Sorry. It is supposed to be "5016x4", the version number. I have corrected it. |
My program