# Questions tagged [matlab]

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.

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131 views

### Locate a number in an array with a special ordering

Below are two examples of arrays (with a special ordering with odd numbers on one side, and even number on the other side) I have, with some given len: ...
87 views

### Counts instances for each category for many Matlab files

This is for machine learning. I have 5 matlab files: AWA, REM, S1, S2, SWS. Each one has 2 arrays: x and y. ...
91 views

### Wavelet decomposition of images

I am working on wavelet decomposition and found a formula for it and wrote it by myself for computation. The formula is: $$I_{LH}(i,j) = \sum_{p=1}^{N_L} \sum_{q=1}^{N_H}\ L(p)\ H(q)\ I(i+p, j+q)$$ ...
1k views

### Optimizing C++ equivalent of Matlab filter function

Minimum working example below. The Matlab filter function filters the input data x using a rational transfer function defined by the numerator and denominator ...
78 views

### Locate a number in an array with ascending even and descending odd entries

Below are two examples of arrays I have, with some given length: For some value z, I want to find the column the value is in. ...
809 views

I have an array matrix, for example A(3,3), I want to make a table with header names like, ['force','mass','acceleration'], the second row contains the units (subheader), ['N','Kg','m/s^2'], and the ...
86 views

### Making interpolations in a 4D matrix

I have Matlab code that is very inefficient and I need to run it several times. The code is basically a big parfor loop which I guess there is almost impossible to ...
337 views

### Running a simulation for all unique combinations of a range of parameters

I have written a script which is supposed to call the function at the bottom for each unique combination of values in the parameter vectors. That function is a simulation which I intend to run over ...
209 views

### Finding shortest distance between a point and a surface using Lagrange Multipliers

I am new to Matlab. Now I need to find the shortest distance between a given point to a surface, which is describe with a function. I am planing to implement the method described in the link below ...
79 views

### Vectorizing Two Sample Kolmogorov-Smirnov test

I'm implementing the Two-sample Kolmogorov-Smirnov test in MATLAB. I must admit I know very little of formal statistics and was simply trying to implement the description in wikipedia's page. Right ...
1k views

### Matlab implementation of Needleman-Wunsch algorithm

This code (an implementation of the path finding Needleman-Wunsch algorithm), given two sequences, correctly aligns and calculates the similarity of them. For example, given two sequences: AAA,CCC ...
1k views

### Benchmarks of various scientific programming languages for theoretical modelling

For a theoretical modelling course for biology students, I am trying to decide which would be the best technical programming language for doing evolutionary simulations in terms of elegance and ...
129 views

### Horizontally concatenating the entries of two matrices, and padding with NaNs

I have two matrices a and b that have, on each line, some values (null or not) and then a bunch of zeros at the end. I want to ...
92 views

### Extract the largest value for each day from a matrix

I have a matrix in which the right-most elements are repeated YYYYMMDD dates in descending order, for example: ...
399 views

### Verification of Sudoku boards

A valid Sudoku board has the following properties The board must be square (n-by-n). Let m = sqrt(n) All rows must contain the numbers 1-n All columns must ...
49 views

### Assign values to a matrix based on the location of non-zero elements in another matrix

I have a matrix, A containing ones and zeros. I want to create a new matrix B where the non-zero elements are in the same ...
121 views

### Merging two square matrices

I would like to optimize a snippet of code, which uses a multiple nested if statements. I am looking for a formula to make it as a combination of multiple arrays ...
1k views

### Pattern recognition and machine learning - Bernoulli mixture model

I have been reading the book Pattern Recognition and Machine Learning (Bishop) for a while, and recently I came across this figure, which was created using Bernoulli mixture model on the MNIST dataset:...
120 views

### Biometric matching score calculator

I'm working on a biometric matching system and I would like to have few suggestions regarding vectorizing the following code: ...
115 views

### Vectorizing a polar coordinate conversion loop in a fingerprint-matching process

I am working on a fingerprint matching technique and it takes a lot of computation time to obtain the result. I am trying to implement the matching process given in A Minutia Matching Algorithm in ...
138 views

### Computing the total different between a pixel and its neighborhood

I have C++ code which written for mex in MATLAB. It used to compute the total different between a pixel and its neighborhood (8 neighborhood in my code). The code ran and gave me an expected result. ...
742 views

### Visualizing Newton-Raphson method for finding zeroes of a function

I have created a program to visualize the working of Newton-Raphson method to find the zeroes of a function: newton.m: ...
59 views

### Quickly Evaluating MANY matlabFunctions

This post builds on my post about quickly evaluating analytic Jacobian in Matlab. The key difference is that I am now working with the Hessian and I have to evaluate close to 700 matlabFunctions (...
797 views

### Converting decimal to Roman numerals using MATLAB

I have written a MATLAB function that converts decimals into Roman numerals. ...
72 views

### Vectorising orthogonal-triangular decomposition for 3D matrix

I am trying to optimise the computation time of my code (for the second time after a first optimisation that gives very good results). Currently, this code is very time-consuming depending on the size ...
779 views

### Reading cell array of vectors with h5py

I have a data stored in .mat files, each .mat contains a cell array of vectors of length ~70. I'm trying to read these .mat files in to Python with h5py, but reading just 1000 cells takes about 7 ...
447 views

### Segmenting brain images (Dicom format) using region-growing algorithm

I have a list of images in a folder where num denotes the index of image and I used num to run the iterations in a "for loop". ...
2k views

### A* search in MATLAB

I have implemented A* search in MATLAB, but I am looking for ways to increase the speed and optimize it. I have tried using a priority queue but I found it doesn't work that well, so I am using a ...
151 views

### Matlab Computer Vision

The code below takes a video as input (a drop onto a fabric surface) and I want it to return the area of the drop. Currently the code works, but I'm no Matlab expert, and wrote it entirely through ...
546 views

### Weighted dice with n faces

Here you find some code that returns the value of a multivariate Bernoulli density function - for a dice with n faces, where each face has its weight (weight must be positive reals, not necessarily ...
538 views

### Linear interpolation Matlab to C++

I don't have a strong mathematics/Matlab background. I would like to convert this Black level correction function from Matlab to C++. Please comment about on the code style and correctness of my ...
81 views

### Function that reorders the columns of a matrix

The objective: Given an m by n matrix, I have written a function in Matlab that reorders the columns of the matrix to output linearly independent columns; other/redundant columns. Basically, it just ...
111 views

### Searching for log entries in SQLite that involve a particular IP subnet

This reads a huge database (SQLite) and extract any IP address similar to ip_base: ...
1k views

### Currying in Matlab

As MATLAB has a hard maximum of 10 input arguments it's possible, but ugly, to implement a curry function in this manner: ...
130 views

### Matlab to C++ percentile clipping

I have a 2D matrix in Matlab and I want to convert the Matlab code into C++. In C++ I have int* channel_gr. The commented code is the original Matlab code. Is ...
66 views

### Plotting a trigonometric function appears to be too slow

This calculates the mobility and it's derivative of one element. If I calculate with 1 value of w, it's very fast. ...
156 views

### Dealing with input and output in Matlab

I just wrote a program which performed some elementary set operations as you can see below. It's the first time I have used input and output of text files so I am mainly looking for critique on that, ...
58 views

### Matlab bins with two features: calculation and plotting

I have the following code in Matlab, which is supposed to do what I asked in this SO question. The idea is to: Divide the temperature deadband of each agent (they are different between agents) into <...
2k views

### fftshift implementation for OpenCV

I'm trying to implement fftshift from matlab for OpenCV. Can you please review the correctness of my algorithm? Have I missed something? Also, is there a better and faster way to do it? ...
3k views

### Simple Priority Queue

I am trying to implement A* search on a grid in MATLAB. I am currently using a priority queue class I found here, but it's a bit slow. I tried to write this simple priority queue class in MATLAB: <...
116 views

### Mean of the squares of differences for a large matrix

I have tried to obtain speed gains by transferring Matlab calculations to C and call it using .mex. My goal is to operate on a matrix $B$ which has roughly the dimension 10000x1000  \frac{1}{\...
415 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: ...
140 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 ...
169 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 ...
48 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 ...
99 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 ...
117 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. ...
281 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 ...