1
vote
1answer
172 views
solving a cubic equation
I need to find the minimum $r$ and the maximum $k$ of the following cubic equation for which there does not exist three distinct real roots.
$rx^3-rkx^2+(r+k)x-rk=0$.
Is it possible to find such $r$ ...
7
votes
1answer
118 views
How do I get a general form for n-th derivative of a function? [duplicate]
I tried the following but it basically returns unevaluated:
...
1
vote
1answer
100 views
Improve performance for finding Fibonacci number which have divisibility property
In this post, the OP requires finding a Fibonacci number having some divisibility property with Mathematica and Maxima. I tired tried that Mathematica code on Mathematica 9.0 and it's still slow ...
12
votes
1answer
95 views
How to instruct FullSimplify to assume that PossibleZeroQ returns correct result?
Sometimes I have a really huge expression that cannot be significantly simplified by FullSimplify. I would like to, so to speak, "simplify with faith" using ...
8
votes
3answers
106 views
What does `: Hold[$IterationLimit]` mean?
In this answer, what does the : Hold[$IterationLimit] part of the following construct do?
...
0
votes
1answer
78 views
joining lists based on content
I have lists created by other processing steps, which are basically constituted by elements like this:
...
0
votes
0answers
76 views
How to highlight a string pattern? [duplicate]
This is an example in the help pages (Working with patterns: Highlight Patterns):
...
2
votes
1answer
108 views
rasterListContourPlot With PlotLegends in Mathematica 9
Jens Nöckel has write functions about (List) Contour Plots with rasterized shading in Mathematica:
http://pages.uoregon.edu/noeckel/computernotes/Mathematica/rasterContourPlot.html
It works well. ...
1
vote
1answer
75 views
Generating a list of specific intermediate numbers associated with continued fractions
First of all, I don't know how ContinuedFraction[] or Convergents[] are implemeneted, and I think it is immaterial to my ...
0
votes
3answers
222 views
Fit line similar to power of trendline in Excel
Is there a way to fit a line similar to power trendline in Excel?
Something in this fashion: Fit[data, {1, x, x^(-n)}, x]
...
3
votes
3answers
69 views
Picking certain pairs according to a condition
I'm a Mathematica beginner and can't find out a solution to my problem. I have a list of pairs of numbers, for example something like this, but much longer: list={{2., 3.}, {3., 2.}, {5., 4.}, {4., ...
1
vote
1answer
52 views
How can I nicely overlay fits for multiple arrays with ListPlot or ListLogPlot?
I'm plotting multiple lists with ListPlot[] or ListLogPlot[]:
ListLogPlot[{ListA, ListB, ListC, ListD, ListE}, PlotRange -> {{0, 100}, Automatic}]
I also have ...
0
votes
2answers
53 views
Automatically evaluating related cells
I have the cells:
In[1]:= l = 2 + 2;
In[2]:= l >= 5
After evaluating them:
Out[2]:= False
Is there a way to evaluate ...
2
votes
1answer
93 views
How can I change the MPS format in Linear Programming samples of Mathematica?
I am trying to play with some linear programming examples of Mathematica as ExampleData[{"LinearProgramming", "blend"}, "Equations"]. It gives me the MPS format of ...
0
votes
1answer
87 views
Reversing axes to get Poiseuille profile [duplicate]
I am trying to plot my velocity profile, similar to this plot (not the arrows, just the shape)
Here is my function
...
1
vote
1answer
56 views
A weird thing about ListPlot3D [duplicate]
I plot the function f(x,y). x goes from 0 to 25 and y goes from 0 to 12.
So, my plot should look elongated since the range of x is twice as long as the range of y.
The problem is that, mathematica ...
2
votes
0answers
42 views
RSolve and incomplete gamma function
I am interested in how Mathematica uses the incomplete gamma function to solve difference equations. For example, if we have this inhomogeneous, 2nd order equation and use ...
7
votes
1answer
147 views
How can I make a cell that contains an image which can be shifted?
When you look at some help pages, they may have cells containing images which are movable within the cell when you left-click and drag the mouse.
Here is a sample: ...
1
vote
1answer
116 views
Confused about Unevaluated
Why does
Map[Unevaluated, Table[PauliMatrix[i], {i, 1, 3}]
give
{Unevaluated[{{0, 1}, {1, 0}}], Unevaluated[{{0, -I}, {I, 0}}], Unevaluated[{{1, 0}, {0, ...
2
votes
2answers
102 views
ODE and BVP: NDSolve errors
The mathematical problem is shown here. I tried to solve writing the
...
2
votes
2answers
152 views
A matrix-vector cross product
I want to do a cross product involving a vector of Pauli matrices $\vec \sigma = \left( {{\sigma _1},{\sigma _2},{\sigma _3}} \right)$; for example, $\vec \sigma \times \left( {1,2,3} \right)$.
...
4
votes
2answers
112 views
Strange behavior of Integrate
I'm trying to calculate the following integral using Mathematica 9.0.1.0
a11=Integrate[Abs[Sin[b+x]],{x,0,2*\[Pi]}]
This should be a simple problem; however, it ...
1
vote
0answers
76 views
Notebook UI: Autocompletion - Display function arguments when typing?
Is there a setting to display the required arguments of a function when typing as Visual Studio, Matlab, etc. does?
0
votes
0answers
5 views
the x-axis is between 0 and L [migrated]
I have a function such as f (x) = 1 + x / L and I would to do graph of this function, where x is between 0 and L (the x-axis is between 0 and L).
8
votes
1answer
160 views
In what situation is the use of Directive required?
Sometimes I see code samples in the document or in this site using Directive, but I haven't yet find a case that Directive is ...
2
votes
1answer
82 views
Expand List Operation
On applying a multiplication and subtraction on a list, like so:
x = 2y - 4;
Where y is a list containing fractions of complex numbers generated from dynamic ...
1
vote
0answers
6 views
Identify the curve from the sample points [migrated]
I am writing a script which will identify the patterns drawn on the touch-pad of the laptop. I have generated all the points where user moved his finger over the touch-pad using synclient.
Now i ...
1
vote
1answer
137 views
How to plot and solve the numerical solution of a integro-differential equation
I have a integro-differential equation of the form
$y'(t) = - \int_0^t {y(t_1 )} e^{t_1 - t} dt_1, {\rm{ t}} \in {\rm{[0,10], y(0) = 1}}$
My code is:
...
5
votes
1answer
121 views
question about Inner
question1:
(code 1 something wrong, Why? and how to overcome this to achieve the next code's effect)
...
0
votes
2answers
58 views
Replace expression using a tuple
Given an expression in x, y, z (for example), and a list with three elements, like ...
0
votes
1answer
72 views
Problem with Replace rules [closed]
I am struggling with a Project Euler problem with Mathematica, what I want to do is to Replace a list like this {5,6,x,x,3} with the rule {x -> i} to {5,6,0,0,3},
{5,6,1,1,3}etc,and here is my code:
...
7
votes
1answer
285 views
FourierSeries for rational function looks wrong
I have the following code:
ser[x_] = FourierSeries[(\[Pi]^2 + a)/(3 x^2 + a), x, 10] // N // Chop
It gives me some series, which I then try to plot. And ...
4
votes
1answer
144 views
3
votes
4answers
121 views
Rearranging a set of numbers
I have this set of numbers, that is a range of prices (ie 6-10) and a quantity of products (5)
...
2
votes
1answer
145 views
Calculate variance of random walk?
How can I symbolically calculate the variance of the following random walk in Mathematica?
Given several discrete random variables such that $p(Z_i=1-2k)=p$, where $k$ is a small real number, and ...
2
votes
1answer
73 views
Cannot run Mathematica C-interfacing examples 'factor'
I am trying to run a Mathematica example concerning Mathematica interfacing issues with C programs. In particular I am trying to call a Mathematica function from C.
Example ...
4
votes
3answers
131 views
How can I combine two Pick expressions into one?
I want to speed up my code, i.e., replace Select by Pick. I think using two Pick ...
0
votes
0answers
41 views
Is it possible to selectively save the calculated values (array) at memory?
My calculation might reach at the limit of my computer's memory because so many output values like the array of a[i,j,k] were produced in the calculation.
In order to retain memory, can be the ...
7
votes
2answers
153 views
Compiling more functions that don't call MainEvaluate
I would like to use Compile with functions defined outside Compile.
For example if I have the two basic functions F and G
F[x_] := x + 2
G[x_] := x
And I want ...
1
vote
1answer
77 views
What does the Error Message in DSolve really mean?
Having this ordinary non linear differential equation
$$y'-x^2 (y+1)\cdot (y+2)^2= 0$$
with the boundary condition $y(4)=2$. When trying to solve this one with Mathematica by using
...
0
votes
0answers
92 views
ode with boundary value problem does not work [closed]
I have to solve the following boundary value problem:
$$
\varphi'(\lambda) + \beta(\lambda) \lambda_x^2 +\gamma(\lambda)\lambda_{xx} = k
$$
where $\lambda$ is a function of $x$ (i.e. $\lambda(x)$), ...
1
vote
1answer
101 views
how to reduce the time to calculate triple integral
i want to evaluate the following integral, but it takes 15 min to do it. i must reduce the time to calculate it, i have to do a table and create a graph, but takes too long.
anyone have an idea ?
...
-5
votes
1answer
44 views
How can I solve this system with Mathematica? [closed]
Systems with 3 equations and 3 unknowns ...
The unknowns are {p,q,j}
...
1
vote
0answers
53 views
Frontend dims out, then freezes while writing output (jpeg)
The frontend dims out and then freezes while Mathematica (9.0.1) exports plots (in jpeg). If I minimize the frontend window and then I bring it back to the front, the window appears grey with not text ...
3
votes
2answers
190 views
Plotting heat equation in a Manipulate expression
I have a 2D heat equation $u_t = \alpha (u_{xx} + u_{yy})$ with conditions:
$u(x, y, 0) = 300$,
$u_y(x, 0, t) = \mu_1(x)$,
$u_y(x, 1, t) = \mu_2(x)$,
$u(0, y, t) = \mu_3(y)$,
$u(1, y, t) = ...
4
votes
3answers
86 views
How to dynamically change the Appearance of a control in Manipulate?
How can I dynamically change the appearance of b? Strangely it works for the Enabled state but not for the Appearance.
Thanks.
...
2
votes
1answer
95 views
Create a table with inline conditions
I am trying to create a table with conditionals inline. For example, I'd like to create a 2 dimensional table like this:
...
2
votes
2answers
77 views
FindFit: Fit that is always lower - Change of Norm?
I am trying to find a fitting function for a multidimensional set of data. I will have to find a fitting function that is always lower (conservative) than the data fitted.
The easiest way is to look ...
1
vote
0answers
66 views
Mathematica 3-D plot (discrete/continous)
I want to visualize a 3-D function in Mathematica, Say F(x,y,z)=0, But there is a small difference here with typical z=f(x,y). Because of it's complexity, I decide to consider the z parameter as a ...
0
votes
1answer
48 views
Don't pollute outside context when solving equation from the outside
This code works fine only if a is not defined in the outside context:
...
