MATLAB is a high-level language and interactive programming environment developed by MathWorks. It is the foundation for a number of other tools, including Simulink and various toolboxes that extend the core capabilities.
9
votes
1answer
302 views
Counting Words in Files - MATLAB style
For my Matlab class I'm taking, I was given the task to write a function ReadAndCountWords that takes in the name of a text file (specifically from this zip file) ...
2
votes
0answers
79 views
Fitness function
I have a fitness function, where inputs x1 to x14 have values between 1:4. Is there a way to make this more efficient? Any ...
1
vote
1answer
32 views
Optimize matlab triple for loop
I have a large matrix samples, I want to make another matrix sampleProb which is the same size, but modified as below:
...
0
votes
0answers
10 views
1/x scaled x axis in matlab plot [migrated]
What is the matlab way to create transformed scaling on the x axis?
I use this workaround to plot an 1/x scaled axis. The problem here is, that plot does not plot ...
4
votes
1answer
62 views
Vectorization for temperature simulation
I'm new to Matlab and I would like to know tips in order to reduce the processing time of such program. The scheme of the actual code is very similar to typical C++ code and I would like to vectorize ...
1
vote
0answers
16 views
Implementation of Logistic Regression
Is this kind of vectorized operations the most efficient way to do this in matlab? Any critics about my code? Am I doing something wrong (i tested several times, I think it works). Notice that I use J ...
3
votes
1answer
31 views
Integrate the product of four infinite series functions
I wrote the following code to integrate the product of four functions.
Two of the functions are hypergeometric functions and the other two are incomplete gamma functions. I have written each function ...
1
vote
0answers
18 views
Iteratively process an identically named file all subdirectories and plot analysis to root directory
This script can successfully go through all of the subdirectories in a root directory, and then process a specific file that exists in all of them and output the file in the root directory as a .png ...
6
votes
1answer
603 views
Using homogeneous coordinates to rotate an image
Currently, I have this code snippet, but it's a little bit slow:
...
3
votes
1answer
159 views
1
vote
1answer
166 views
Creation of MxM matrix: Python version much slower than Matlab version
I have written the same code in Python (NumPy) and in Matlab, and I tried to use the same structure for both language and follow the same procedure. Now my problem is that when I run my code in Python ...
3
votes
3answers
453 views
Presidential election predictor using matrix-processing
I'm currently working on a project where I am trying to predict a presidential election based on the population density and region of a voter. I wrote a few MATLAB functions to parse the data, but it ...
2
votes
0answers
45 views
Speeding up loop-rich Matlab function to calculate temperature distribution
I would like to speed up this function as much as possible in Matlab.
This is part of a bigger simulation project, and as it is one of the most called functions within the simulation, this is crucial.
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3
votes
2answers
68 views
Improving Matlab function within big simulation
I have a very big Matlab simulation project in my hands, which I wanted to optimize, since I'm running it many times to tune parameters and the like.
Using Matlab's ...
3
votes
1answer
121 views
1
vote
1answer
49 views
Improving excution time for list and sampling in Python
Here is my code for generating edge list based on Price model algorithm. I think there have two points to reduce execution time:
use proper data type
use faster random sampling
Originally, I used ...
3
votes
1answer
695 views
Run length encoding of vectors in MATLAB: looped version and vectorized version
A project I'm working on requires something akin to run length encoding on a vector in matlab. The data is in the form of a numeric vector, and the output is in the form of two vectors, ...
1
vote
3answers
74 views
Using matlabpool: Is my embedding correct?
A general question: For using matlabpool, I write the line
matlabpool open local 12;
as the first line in my code and the line:
...
3
votes
1answer
1k views
Build a combinatorial matrix from two vectors
I want to define a matrix of values with a very simple pattern. I've achieved it with the code below but it's ugly - very difficult to read (I find) and surely not as optimal, in terms of performance, ...
5
votes
1answer
158 views
Processing random matrices
I am doing my research about scheduling by using Matlab. I am a new Matlab user and I have a problem with time execution of my following code:
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6
votes
3answers
2k views
Speeding up this k-nearest neighbors implementation
I have implemented kNN (k-nearest neighbors) as follows, but it is very slow. I want to get an exact k-nearest-neighbor, not the approximate ones, so I didn't use the FLANN or ANN libraries.
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1
vote
0answers
34 views
Simple class container for hdf5 files
I implemented a simple class container for hdf5 files in matlab.
The situation is as follows. Measurement data is saved in hdf5 ...
3
votes
1answer
931 views
Legendre's polynomials and functions
I would like to improve this function to reduce the run time and optimize it.
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1
vote
0answers
103 views
Efficient C Code Alternative to MATLAB's im2col
The function im2col in MATLAB is very useful to vectorize Patch based Image Processing algorithms.
The problem is the function isn't optimized and doesn't use C ...
1
vote
2answers
120 views
Using brute force to find an energy optimal path for a given amount of time
The code below implements a brute force method to find an energy optimal path for a given amount of time t_aim using recursion (the recursion function is ...
4
votes
2answers
2k views
Trapezoidal rule to approximate the integral of x^2
I've implemented the trapezoidal rule to compute the integral for a function \$x^2\$. I would like to see another style of the same code. It seems Matlab hates for a matrix to be expanded without ...
2
votes
0answers
65 views
Kullback-Leibler (KL) distance between inside and outside contour code
I am trying implement the distance measurement between two distributions. The detail is described in here and input image . Let short summarize the idea of the paper:
The input image is divided ...
2
votes
2answers
106 views
90 year data simulation in need of performance increase
I developed some code for my masters project that will simulate 90 years daily data using 1000 different data sets. The code is working fine and gives the correct output that I wanted but the ...
4
votes
1answer
124 views
Vectorize Matlab sum
I have the following Matlab function:
function [res] = a3_funct(x)
res = 0;
for i = 1:size(x,1)
res = res + abs(x(i))^(i+1);
end
end
It's ...
3
votes
0answers
363 views
Satellite orbit simulation in Matlab using Runge Kutta 4
I have a satellite orbit simulation in Matlab (Using Runge Kutta 4). It seems ugly and I don't know how to fix it.
fx.m file:
function v = fx(t,x,vx)
v = vx;
...
8
votes
1answer
122 views
Verifying boardgame mathematics with MATLAB
I recently bought this math-based boardgame for my little cousins, and am now trying to verify its design with some MATLAB code. The relevant parts of the game are:
A board with numbers from 1 to ...
1
vote
1answer
464 views
Computing the sum of squared differences of the concentration profile
About Data: I have a 3D data (100x100x20) of space and time (c) where first 2 dimensions are concentration values along space while 3rd dimension contains ...
2
votes
0answers
34 views
Avoiding boundaries if-cases when filtering image matrix
I have the following MATLAB Code which I want to optimize.
It's related to an image matrix (2D) which I want to filter.
Though it is MATLAB code, the same problem would arise in C code.
The problem ...
1
vote
0answers
41 views
Why does lu-factorization make my program slower?
I'm trying to calculate the smallest eigenvalue of the matrix A by using the "inverted exponentiation method" (see the code). I manage to find the smallest eigenvalue, but when I try to optimize the ...
3
votes
1answer
50 views
Using the Return Value of a Function to Select an Element in a Struct Array
I'm learning MATLAB (still trying to "think in vectors") and have the following piece of code:
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2
votes
1answer
45 views
Less For, more MATLABesque?
I have written a piece of MATLAB code that (hopefully) calculates CECT. I have two matrices of psychophysiological measures - one for brain data, one for heart rate; both are of the format epochs * ...
0
votes
0answers
289 views
Stochastic gradient descent squared loss
I have implemented stochastic gradient descent in matlab and I would like to compare my results with another source but the error I am getting is higher (I am using squared error). I am worried I am ...
2
votes
3answers
84 views
Is this a valid way of computing autocorrelation?
I am a beginner in Digital Signal Processing and I was trying to compute and plot an autocorrelation.
I've wrote this piece of code:
...
4
votes
2answers
70 views
What's the fastest way to get the points I want out of a huge blob?
In MATLAB I have a set of 5393280 points in the form of a decimal-valued vector (x,y,z). How do I represent them in a way that I can quickly collect all the points within some rectangular x-y domain?
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4
votes
1answer
4k views
K-nearest neighbours in MATLAB
I implemented K-Nearest Neighbours algorithm, but my experience using MATLAB is lacking. I need you to check the small portion of code and tell me what can be improved or modified. I hope it is a ...
2
votes
1answer
406 views
Parsing MWNumericArray to C# code optimization
This is my function returning matrices from Matlab. This code run very slowly.
I was trying to use Parallel.For in-order to run it in parallel threads but I got ...
2
votes
0answers
96 views
Increasing speed of parity check matrix
The code runs fine and takes 100s to complete it for 5 iteration. I need to reduce it to take less time with the same number of iterations.
h = 324 by 648 matrix
The code is that of FFT Belief ...
2
votes
1answer
8k views
Matlab code demonstrating use of fft (Fast Fourier Transform)
I posted the following Matlab script in response to a question on Signal Processing. Here is the questions with my answer.
I am looking for comments on how to make this code more instructive for the ...
3
votes
1answer
178 views
Calculate FFT from windowed time-based signal
I have a time-based signal (Raw signal) sampled at 6 MHz and need to analyze it in freq. domain.
I'm learning DSP and this is very first time I work with DSP. Could you please help to check if this ...
1
vote
1answer
77 views
Speeding up repetitive initialisation with structured data?
I need to speed up this code: it creates a multilinear function. I considered the below methods but no idea which with the largest benefit.
replacing dummy variables with things such as anonymous ...
1
vote
1answer
78 views
How can these if-else statements be made more efficient?
I am using the cURL tool in MATLAB 2013b with Ubuntu to download a whole bunch of files. The files have one of three possible versions: 1.0.0, 2.0.0, or 2.1.0. Using the HTTP, I first check the ...
3
votes
1answer
274 views
Speed up for loops _ Set of linear equations
I have N^2 matrixes. Each one is a 3x3 matrix. I want to concatenation them to a 3Nx3N matrix. I know that the big matrix is symmetric. Evaluation of whole 3x3 matrixes are time consuming so I want to ...
5
votes
2answers
1k views
Python / Numpy running 15x slower than MATLAB - am I using Numpy effeciently?
Here is some code I wrote in Python / Numpy that I pretty much directly translated from MATLAB code. When I run the code in MATLAB on my machine, it takes roughly 17 seconds. When I run the code in ...
1
vote
1answer
808 views
Matlab - Fastest way to parallel read many files line by line?
I have a few hundred files in a directory that I need to read in parallel. Namely, the files that have the same name, but different file extensions (.a and .b), but they're pretty much plain text ...
2
votes
2answers
1k views
MATLAB and Armadillo, hints on translating
i'm rewriting some Matlab code to c++ using armadillo, a libs for linear algebra. really good libs, IMHO. but i had to translate some matlab construct because armadillo isn't matlab.
i want to share ...
