Questions tagged [warning-messages]

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2
votes
1answer
57 views

Getting error Solve::units [closed]

I'm trying to solve the following formula for i, given values for all other variables. There are two equations, the first one is a formula to show the transit ...
6
votes
2answers
704 views

What is the reason for failing to solve the following equation?

I have a simple differential equation $$ \frac{df(T)}{dT} = g(T)(f(T)-f_{\text{eq}}(T)), $$ where $g,f_{\text{eq}}$ are some smooth functions, and $T$ is an analog of time, but the evolution ...
1
vote
1answer
122 views

Find minimum of a function defined via NIntegrate [closed]

I need to find the minimum of a function f(t) = int g(t,x) dx over [0,1]. I used g[t_, x_] := *huge expression* f[t_?NumericQ] := NIntegrate[g[t, x], {x, -1, 1}] ...
5
votes
1answer
226 views

Step size is effectively zero

I've been trying to solve Bodewadt flow equations which is a system of differential equations. $$\begin{align*} F^2 - G^2 + HF' - F'' + 1 &= 0 \\ 2GF + HG'-G'' &= 0 \\ 2F + H' &= 0 \end{...
0
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0answers
60 views

How to solve this linear complementarity problem with NDSolve or other functions? The arguments should be ordered consistently

I want to find a numerical solution of $\omega(t,q)$, where $t\in[0,T]$ and $q\in[0,N]$. $q_t$ is a determinstic w.r.t $t$, other unmentioned parameters can be fullfilled or given by the user. I met ...
4
votes
1answer
79 views

Result is correct, but LinearProgramming spits out lpnn warning in RegionPlot

Sorry if this is a newbie question. I wrote a function to decide if a given vector is in the convex hull of another set of vectors using linear programming. ...
1
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2answers
114 views

What makes a system be differential-algebraic equations?

I am trying to solve the equations in the following way: ...
0
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0answers
36 views

How to avoid machine underflow for plotting and integrating?

I am trying to integrate the following integrand, which I have plotted: ...
0
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1answer
188 views

" Unable to find initial conditions that satisfy the residual function within specified tolerances"

I know that there are similar questions on stack exchange. However, I am relatively new to mathematica, so I couldn't really understand the answers. Sorry. Here's my code: ...
0
votes
1answer
64 views

Error message when solving simultaneous differential equations

I am trying to solve the following set of differential equations to obtain $\phi[t]$, $y[t]$, and $z[t]$. The 3 differential equations are here: ...
2
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4answers
319 views
1
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0answers
58 views

Evaluate the NDSolveValue at the condition point with replacement [closed]

I try to Evaluate something with replacement ...
1
vote
1answer
81 views

How to replace the expression in nest?

I need to calculate the following function with replacement in recurrence ...
1
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2answers
94 views

Confused by result of NDSolve for Second-Order nonlinear ODE

It is impossible to solve numerically a nonlinear second-order equation, although the initial conditions are given. ...
2
votes
1answer
191 views

(Numerical) calculation of nested integrals

The problem I'd like to (numerically) compute nested integrals of the type $$I(a;k) \equiv \left( \prod_{i=1}^k \int_0^\infty \mathrm{d}x_i \right) \exp \left( - \frac{1}{4a} \sum_{i=1}^k \left( x_i - ...
1
vote
1answer
46 views

Getting message Set::setps: Kpr[x,y] in the part assignment is not a symbol

I use a loop to create a set of matrixes Subscript[k[x, y], i], depending on variables x, y. Then I create a large matrix ...
3
votes
0answers
44 views

Behavior of $MinPrecision seems to have changed between 12.0.0 and 12.1.1

I am running into a very weird bug where setting $MinPrecision to some value (in this case 200) has a very different and ...
0
votes
0answers
22 views

All formatting lost from a working notebook

I had a working notebook with title and normal cells. I opened and all cells were merged to a normal (InputformDisplay type) cell, all titles and text cells are lost, that is, they became the same ...
1
vote
0answers
58 views

Need help with NestList [closed]

NestList::intnm: Non-negative machine-sized integer expected at position 3 in NestList[#1 + t&, 0, 8.]. What does the above error mean and how can I refer to result of ...
0
votes
1answer
100 views

Why DSolve cannot Find a General Solution for this ODE?

The Problem Given a mass m=1 moves in potential V(x)=|x|^3; and x(0)=1,x'(0)=0; So I set up ...
0
votes
1answer
90 views

Having problem in evaluating the eigenvalues of an $11\times11$ symmetric matrix in Mathematica [closed]

I am solving an $11\times11$ matrix in Mathematica. I am facing problem when I try to find the determinant or eigenvalues of this matrix. The error (Det::matsq/<...
0
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0answers
59 views

SystemException["MemoryAllocationFailure"] in Integrate

Integrating products and ratios of piecewise linear functions throws the error ...
2
votes
1answer
65 views

DSolve implicit function of time

Apologies for the basic question. I am trying to solve this differential equation for $w(t)$ as a function of $q(t)$: $$ \frac{dw(t)}{dt} = \mu_v \frac{R_{on}}{\delta} \frac{dq(t)}{dt}. $$ Solving ...
1
vote
1answer
36 views

Error message when referring to the value of a part of one element in a list [closed]

The following works fine to define an element of a two-argument list: T[1, 2] = {3, 4, "yes"} But when I try to change the third part, like this ...
1
vote
1answer
38 views

Manipulate giving errors when I plot the product of a step function and a continuous function

Riemann's prime counting function J (link) takes half-values at every jump-discontinuity. So, I define it thus: ...
2
votes
0answers
56 views

Problem with stopping NDSolve after a condition is met

I'm trying to write a piece of Mathematica code that is essentially a differential equation solver that needs to take a specified function $V[t,q]$, and then numerically solves the differential ...
1
vote
2answers
232 views

Error message: "-1.99992 cannot be used as a variable" [closed]

could anyone please tell me how to fix this: I want to plot the solutions of a coupled ODE: $\frac{1}{3} u\partial_x ^3 u = \frac{1}{2} \partial_x v; \ \partial_x\left( u \partial_x v - \frac{1}{2} u^...
0
votes
1answer
90 views

Integral involving orthogonal functions (quantum harmonic oscillator eigenstates)

I have a question about the capabilities of the Integrate command for general parameters. We know that there is a system of functions: ...
0
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0answers
56 views

Serious Startup Error: Error code 603. What to do?

So my laptop shut down due to lack of battery with some open Mathematica notebooks that were saved but now Mathematica wont launch at all and I cannot find anywhere information about this error code. ...
0
votes
1answer
85 views

Why is this integral throwing a "MemoryAllocationFailure" error?

The following call to NIntegrate throws the error: Throw::sysexc: Uncaught SystemException returned to top level. Can be caught with Catch[[Ellipsis], ...
0
votes
2answers
101 views

How to know, which constraint is being violated in linear programming problem?

my task is to minimize costs of dispatching various power plants in order to meet demand in a transmission grid. I solve the task as a linear programming problem with the help of Minimize[] function ...
0
votes
0answers
68 views

How to fix a ParametricNDSolveValue? - Encountered non-numerical value for a derivative at t == 0

How to fix a ParametricNDSolveValue? - "ParametricNDSolveValue::ndnum: Encountered non-numerical value for a derivative at t == 0." I have tried ...
0
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0answers
26 views
0
votes
2answers
63 views

Syntax error using Plot

Why is the error coming and what should I do to resolve it The code is ...
2
votes
5answers
139 views

Can't be solved using methods available

I'm stuck on this and chagrined I'm even asking, but this: ...
4
votes
2answers
161 views

Finding the number of even numbers in Pascal's triangle (code gives memory error)

I have the following code: ...
0
votes
0answers
59 views

InitializeBoundaryConditions::fembdnl: The dependent variable in the boundary condition needs to be linear [duplicate]

Checking the documentation on the error were of not that much help to me. Can someone please suggest how to deal with it? ...
2
votes
1answer
77 views

When does NDSolve issue zero step size error NDSolve::ndsz?

I want to detect directly when step size becomes "effectively" zero. The below example from the documentation throws the error message as expected: ...
1
vote
0answers
43 views

avoid using protected variable names in defining static pure functions

I will provide one example to show what the problem is. Collatz[m_] := Collatz[m] = 1 + If[EvenQ[m], Collatz[m/2], Collatz[3 m + 1]]; Collatz[1] := 0; this ...
0
votes
1answer
80 views

DSolve for System of Non-Homogeneous Differential Equation

Solve: x' = Ax + b Given: A = {{1, 2}, {3, 4}}; b = {{e^{t}},{2}}; This will solve if b == 0 DSolve[{x1'[t], x2'[t]} == a.{x1[t], x2[t]}, {x1[t], x2[t]}, t] But if ...
0
votes
0answers
108 views

the number of equation does not match the number of variables

Excuse me , can you help me , please ? When i make run for this programme it give me a wrong that the number of equations does not match the number of variables ,,,, I try a lot on finding the wrong ...
1
vote
0answers
50 views

Errors with assigment and no errors with replacement rule, why? [closed]

So I have an expression, let's call it f11 which is a function of t of this form f11= a1*t^(-4)+ a3*t^(-3)+... and so on up until a finite positive power of t. In ...
0
votes
1answer
66 views

Getting error when I substitute PDE for ODE

The following code works perfectly: ...
6
votes
1answer
144 views

NDSolve: how the initial step of finding explicit derivatives can be avoided?

There are several posts here devoted to resolving the following error message of NDSolve (NDSolve::ntdvdae, ...
1
vote
0answers
52 views

NIntegrate with AdaptiveMonteCarlo method

I have some complicated function that depends on a few parameters that I need to integrate. It is integrated in the fastest way by using "AdaptiveMonteCarlo" method. However, I have found ...
7
votes
0answers
50 views

BarChart does not display asymmetric error bars correctly

BarChart seems to read the uncertainty in elements the other way around. The object: Around[5, {1, 10}] is evaluated as . However, when you use it in a BarChart, the uncertainties are swapped: ...
1
vote
2answers
110 views

Maximize: x in Vectors[5, R] is not a valid variable

I am learning how to do optimization with a variable number of variables in Mathematica. I tried to write one experiment that I need to do but I have failed to get even a stripped-down version working....
0
votes
0answers
46 views

Part::partw: error in Custom Spline Algorithm

I am attending a Calculus course where we use Wolfram as a supporting tool, and I was trying the algorithm provided for Spline interpolation and I get the error in the picture: ...
4
votes
1answer
55 views

Looking for an explanation of unusual behavior in Divisors[] function

I have defined the function that counts the number of square divisors of input integer x. The function is ...

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