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Nov
14
comment Linear Stability Analysis Routine. Normal Modes in NDSolve
In your function eqn1[] and eqn2[], here is an random example from google search mathematica.stackexchange.com/questions/34945/… again, this is something to try, I am not saying it will solve the problem, since I do not know what the problem is :)
Nov
14
comment Linear Stability Analysis Routine. Normal Modes in NDSolve
Just a wild guess, try to add ?NumberQ to the definitions of all the functions arguments for functions called/used by NDsolve. (can't follow your code and try it, since no MWE provided).
Nov
14
reviewed Approve suggested edit on Solving recurrence relationship using iteration
Nov
14
comment Solving recurrence relationship using iteration
Are you saying that input at time i depends on input at time i+1 ?? Normal recurrence is where future values depends on past values, this way the system can be initialized correctly.
Nov
14
answered Add a letter to a variable name from a list
Nov
14
answered Pattern matching in nested lists
Nov
14
revised Fourier-Analysis How to display every period correctly?
deleted 38 characters in body
Nov
14
answered Fourier-Analysis How to display every period correctly?
Nov
13
comment Solving a system of nonlinear equations?
Are you saying all this hard work to come up with some solution and I was using bad equations to start with? oh well....next time I'll avoid Chemistry questions ;)
Nov
13
answered Solving a system of nonlinear equations?
Nov
13
comment Solving a system of nonlinear equations?
You have 7 equations, but I keep counting only 6 variables. If you get rid of one equation, it will help.
Nov
12
comment Numerically solving a system of PDEs where one function is composed with the other
DO you have a reference or published examples of such PDE's? (I mean of similar form) to give one an idea of how they can come about.
Nov
12
comment Numerically solving a system of PDEs where one function is composed with the other
... NDSolve::cdelay: The method currently implemented for delay differential equations does not support delays that depend directly on the time variable or dependent variables. so if the same system is not valid to be solved analytically (mathematically speaking), how could it becomes valid to be solved Numerically? (I'd have to ask my teacher when I go to school tomorrow on this and see what he says about this).. either way, what you are to do does not seem to be supported by direct use of NDSolve...
Nov
12
comment Numerically solving a system of PDEs where one function is composed with the other
I do not think the error message is right. I think the pde itself is not valid mathematically speaking. You have a dependent variable being treated as independent variable. One can see this more clearly in this example: Clear[u, v, x]; eq1 = u'[x] == u[x] - v[x]; eq2 = v'[x] == u[v[x]]; DSolve[{eq1, eq2}, {u[x], v[x]}, x] the error is DSolve::nestdv: "The expression v[x] has nested dependent variables". Now switch to NDSolve, same system, and now you get the delay error: NDSolve[{eq1, eq2, u[0] == 0, v[0] == 0}, {u[x], v[x]}, {x, 0, 1}] and the error is ...
Nov
11
answered NDSolve - 2nd order ODE - how to solve for y and y'
Nov
11
answered Find a notebook I had open recently
Nov
11
comment Strange result for the analytic integration leads to Hypergeometric2F1
"So can I trust the result?", well, I would not myself until I make sure I know what is going on. Since Maple gives different result, and since substitution gives different result than expected, this needs to be resolved first. I just tried it on Maple 17 for some values, Maple gave -1.73, and M gave -0.317. Screen shot: !Mathematica graphics So wait until someone knows more about these special functions and can suggest something? Notice how Maple used the csgn() function in its answer. I am no expert in these special functions and branch cuts..good luck
Nov
11
comment Strange result for the analytic integration leads to Hypergeometric2F1
It seems to do with a branch cut. The first Integrate did not know the value(s) that y can take, so it made a decision, and the second example, y was known, so this problem did not show up. By the time the integrate was finished, it was too late. Hence the substitution of same value for y did not give the same answer as the second Integrate. Adding Assumptions did not seem to help.
Nov
11
reviewed Approve suggested edit on Solving a system of non-linear differential equations
Nov
11
comment Solving a system of non-linear differential equations
..."MaxSteps->Infinity" this one is easy. Mathematica gave an error saying Maximum number of 10000 steps reached at the point t == 1.5727575203, so you just increase the number of steps and hope for the best.