MATLAB = MATrix LABoratory A scientific computing/programming software originally developed at the University of New Mexico and designed with particular emphasis on vector and matrix based operations.
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What is the Complexity of MATLAB operations
I'm trying to analyze the complexity of MATLAB code I wrote.
I'm trying to figure out how much (in terms of $O$ or $\Theta$) to give functions like find, matrix ...
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1answer
72 views
Integration of an indefinite integral: matlab precision problem
The integral I need to evaluate is:
$$ \int_x^{\infty} \frac{t^n}{e^{t} -1} dt $$
After some research I found a paper saying,
The numerical values of the two integrals [...] are easily ...
4
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1answer
46 views
Matlab help related with the scaled newton's iteration method
I apologize if this question doesn't fit for this site. I am new for this site. I need little help with matlab code for the method mentioned in this paper for computing the inverse of the matrix.
In ...
2
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1answer
40 views
How to save a matlab source code into a string in matlab?
I want to save a matlab source code into a string format in matlab. Does anyone know how to do this? For example,
type xxx.m
can display the source code of xxx.m. ...
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1answer
71 views
How can I compute whether a sequence is an even or odd permutation of an increasing sequence? [closed]
Variants of this question have been crossposted to Stack Overflow and Mathematics Stack Exchange. Additional answers may be found at these other sites.
Computational Science People:
I originally ...
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1answer
158 views
Implementing Explicit formulation of 1D wave equation in Matlab
So the theory is straightforward. We have:
$$\frac{\partial^2U}{\partial t^2}=c^2 \frac{\partial^2U}{\partial x^2}$$
discretizing it gives:
$$\frac{U(i+1,j)- 2U(i,j) + U(i-1,j)}{(\Delta t)^2} = c^2 ...
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vote
1answer
48 views
Discrete 3D convolution of matrix valued functions
As stated in the title, I need to make a discrete 3D convolution of two matrix-valued functions. Or, actually, I need to convolve a matrix-valued function with a vector-valued function. That is, I ...
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1answer
66 views
Solving a “generalized” linear programming problem
I need to solve the follwing constrained optimization problem. Is there any MATLAB
toolbox which can solve this.
minimize $A_1 x$
subject to $A_2 x = 0$
$A_1$ is an $m\times n$ matrix where $m ...
7
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2answers
141 views
Caching mechanism
I've been having problems designing an effective caching mechanism.
The mechanism is to be used as part of a project developing scientific software.
The goal is to save computation time by loading ...
1
vote
1answer
42 views
matlab set center of output figure to [0 0 0]
I have a few set of data of three dimensional matrices, n x 3 with x, y and z coordinates.
I viewed the matrices in the figure window.
...
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0answers
74 views
Block Cyclic Reduction implementation help, matlab
I'm sorry if this question is too open ended, or not appropriate for the forum. If so I'll remove the post and see if I can refine my problem, but at the moment I'm totally stumped.
I was hoping ...
2
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2answers
77 views
Matlab element within ranges and distance between two points
I have a 53534x3 matrix with x, y and z coordinates.
I want to find the element of matrix within ranges as follows:
...
3
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1answer
59 views
How to do local FFT on huge 3D vector data cell mesh and visualize it spatially?
Simulation type:
I'm running a simulation with the OOMMF micromagnetics package
http://math.nist.gov/oommf/
where are magnet is represented by a mesh of 3 million cells, it gets excited by a ...
6
votes
1answer
129 views
How to approximate the condition number of a large matrix?
How do I approximate the condition number of a large matrix $G$, if $G$ is a combination of Fourier transforms $F$ (non-uniform or uniform), finite differences $R$, and diagonal matrices $S$?
The ...
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votes
2answers
138 views
Finding A and X such that AX = 0, X is positive non-zero, and A is sparse
I apologize if this is a naive question. I'm trying to create some boostrap data for a system of linear, ordinary differential equations at steady state.
Since the equations represent the ...
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0answers
52 views
Sign or cardinality constraint when solving for sparse signal?
I'm currently learning about using linear and semi-definite programming to find sparse solutions to problems. In particular, finding sparse solutions where the sampling functions are sinusoidal ...
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2answers
69 views
Matlab : Is there a way to programatically safely halt code execution (like FORTRAN's stop)?
Like the title says, I want to be able to stop the code at a specific location and have it halt safely. I cannot find a command to do it like for example in FORTRAN there is the stop command.
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1answer
56 views
GMRES Matlab 'tol' parameter
I need to use GMRES solver in MATLAB, and I need to play around with the codes parameters and I had a very simple question about its usage.
The documentation of the solver here mentions a parameter ...
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0answers
59 views
features recognition & reconstruction of 3d mesh delaunay matlab
I managed to display the coordinates of x,y and z into a 3D mesh by using delaunay function. The coordinates are in .obj format actually and i have read it into matrix form.
Now, i would like to ...
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0answers
47 views
Issues with sequential feature selection
I am trying to do some feature selection in gene expression data with 22215 features. I followed the tutorial here.
I initially applied filter method(ttest) to select the features having the best p ...
0
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0answers
14 views
How does the Trimulus sensitivity functions relate to the luminosity function?
In colorimetry, the irradiance spectrum is weighted with the luminosity function to obtain the perceived luminosity, and the tristimulus sensitivity functions to obtain the perceived ...
3
votes
1answer
166 views
in matlab, what differences are between linsolve and mldivide?
in matlab, both linsolve and mldivide are used for solving a system of linear equations, in all of determined, overdetermined and underdetermined cases.
Reading their documents, I was wondering what ...
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0answers
16 views
Matlab SISOtool Plotter
Is anyone familiar with plotting in the Matlab SISOtool? For some reason, I cannot access the plot options to change the plot thickness. Specifically, I am trying to play around with the line ...
2
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1answer
27 views
Trying to implement a simple/efficient combinations function in MATLAB
So, recently, I have found myself in the position of having to implement a combinations function in MATLAB. What I mean by this is the following: I simply need to list all possible combinations for an ...
4
votes
2answers
101 views
Testing 1D Poisson Solver
I'm trying to test a simple 1D Poisson solver to show that a finite difference method converges with $\mathcal{O}(h^2)$ and that using a deferred correction for the input function yields a convergence ...
4
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1answer
93 views
Implementing the $\theta$-method for solving an IVP
I also posted this question on the Math SE site, but it was suggested I post here also.
I want to implement the $\theta$-method to solve an IVP in MATLAB. The $\theta$-method is:
$y_{j+1} = y_j + ...
0
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1answer
92 views
How easy is it to combine symbolic and numeric computation in Matlab?
CS Beta people:
I have been doing some multiple integrals with a combination of symbolic and numerical integration (because symbolic answers have not always been possible). I have been using ...
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0answers
27 views
Left and right eigenspaces of product of grammians
I solve the Lyapunov equations :
$$ A W_C E^T + E W_C A^T + B B^T = 0 $$
$$ A^T W_O E^T + E W_O A + C^T C = 0 $$
to obtain $ W_C $ and $W_O$. My aim is to get the left and right eigenspaces of $W_C ...
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1answer
200 views
can I trust this numerical triple integral from Matlab?
Computational Science people:
I originally posted this question at Math Stack Exchange and someone commented that I might get "much better" answers here:
I am a novice at numerical methods and ...
1
vote
0answers
69 views
setting a condition on MATLAB ode45 output
I want to solve a system of differential equations using ode45 , for (many) parameters in MATLAB to investigate the behavior of solutions with coefficients of the equation .I want to find the ...
6
votes
4answers
165 views
parameters estimation
I have to estimate a parameter (K), but I don't know how I can do it. I think by a regression model (minimum least square?), but I'm not sure. The system is:
...
2
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1answer
318 views
Finite Element Method: 2-D Poisson's Equation in Matlab, Gaussian quadrature
I'm having trouble understanding how to code 2-D Poisson's Equation with Dirichlet boundary conditions. What I have thus far is
Constructed square mesh with triangular elements
Assembled stiffness ...
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1answer
70 views
Order of MATLAB FFT frequencies
This wikibook states that the output of MATLAB's FFT corresponds with the wavenumbers ordered as:
...
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1answer
104 views
how to know cylinder volume in pixels?
I have a 3D point cloud representing ad object. I use a 3D cylinder to fit this object in the point cloud, so I check if each point is inside the cylinder and, if it is, then I assign a weight to that ...
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2answers
95 views
I'm having trouble debugging multigrid. What to do?
I've spent far too much time coding and debugging multigrid. While I clearly can't post all of my code as it would be silly to ask someone to go through all that code, is there anything I should pay ...
4
votes
3answers
92 views
PRIMA gives an unstable result?
I am working with Modified Nodal Admittance representation of circuits. I am doing Model Order Reduction using PRIMA on MATLAB. I am considering these circuits as Descriptor State-Space systems.
I ...
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2answers
67 views
numerical investigation of stability of motion (confinement)
I am trying to find the required specifications of a RF trap, in which a proton can be confined.(trap dimensions,voltage frequency and amplitude used, etc). I have to solve the equations of motion ...
4
votes
3answers
356 views
Efficient assembly of finite element matrix in MATLAB
Question
What is the most efficient algorithm for finding a row of a matrix which matches a given row? This is the same as a table lookup based on multiple criteria.
Context
Finite Element Matrices ...
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votes
6answers
355 views
Soft Question: Where does Python fit into the picture?
So I've been debating whether or not I should bother learning Python. From speaking with my professors, Matlab seems to be the common language used in applied mathematics/computational science as far ...
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3answers
366 views
Method for numerical integration of difficult oscillatory integral
I need to numerically evaluate the integral below:
$$\int_0^\infty \mathrm{sinc}'(xr) r \sqrt{E(r)} dr$$
where $E(r) = r^4 (\lambda\sqrt{\kappa^2+r^2})^{-\nu-5/2} ...
2
votes
1answer
60 views
Customizing Genetic Algorithm on Matlab
The Matlab version is 2012b. I am trying using the built-in GA functionality through the Optimization Tool GUI on Matlab. I want to use bit string chromosome with a given length (for example L=24) and ...
0
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1answer
117 views
software request for solving acoustic wave equation
I am searching some libraries or toolboxes (preferred MATLAB) for solving acoustic wave equation in heterogeneous media with time varying source term, i.e. $$\nabla^2 \psi(\vec{r},t) - ...
4
votes
2answers
152 views
How to code in Matlab: If an argument is empty, then default to “x” value?
I have a function with a number of arguments, but some of them are optional.
1.) If when the function is called, some are left empty, how do I code it so that it defaults to a specific value?
2.) ...
3
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2answers
87 views
Handling function inputs in Matlab
Say I have a function
function u = somefxn(f,n)
where f is some function, say ...
6
votes
1answer
111 views
Nonlinear dynamics: algorithm suggest
I've just started a thesis on nonlinear dynamics which entails numerical analysis of the Duffing oscillator (DO). It's basically just a second order ODE, or equivalently a set of ODEs.
Say, after ...
2
votes
1answer
102 views
What is the runtime complexity of MATLAB operation A*B where A and B are general sparse matrices?
I tried to search the answer and I found that method cs_multiply from this book has been adopted for the purpose of multiplication of two general sparse matrices in MATLAB.
In the book it says that
...
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1answer
74 views
Clustering data based on the radius of a sphere
I have a data-set that has four columns [X Y Z C]. I would like to find all the C values that are in a given sphere centered at [X, Y, Z] with a radius r. What is the best approach to address this ...
4
votes
1answer
128 views
Creating spheres In Matlab that change surface color depending data
I am trying to create a series of randomly distributed spheres in Matlab, three will be three sub-sets. I would like each subset to have a different color. I am using a structure because each sphere ...
3
votes
1answer
73 views
Simple substitutions using symbolic computing in MATLAB
Suppose I have the following MATLAB code.
syms a b c1 c2
c1 = a + b + pi*b
c2 = a + b + 0.5*b
Then c1 gets evaluated to ...
3
votes
2answers
85 views
Are matlab C library versions backwards compatible?
I have some C++ code that links to matlab2008b. Are matlab 2012a and 2012b backwards compatible with 2008b?
If it's not trivially compatible, are there some simple steps to make it compatible?
