# Tagged Questions

MATLAB is a high-level language and interactive programming environment for numerical computation and visualization developed by MathWorks. MATLAB can be used when performing tasks such as signal processing and communications, image and video processing, computational finance, and computational ...

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### Generate two matrices such that multiplication of these matrices results a symmetric positive definite matrix

I want to generate a tall&skinny matrix and a fat&short matrix, such that multiplication of these matrices results a symmetric positive definite matrix. My inefficient/expensive solution is: ...
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### Delaying signals in Matlab

I'm new to MATLAB and have a question that I need help on: The problem I have is to plot the simple signals: a 1Hz Sine wave, a standard rectangle function and a standard triangle function Here is ...
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### MATLAB: how to include running time on a graph? [closed]

I have a MATLAB/Octave program for which I used the tic and toc functions to measure the time elapsed for some calculations. e.g....
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### Did I implement a log-normal distribution incorrectly?

I have a bunch of data relating to the lengths of certain objects. I found out that the log of these lengths are somewhat normally distributed, so I used a lognormal distribution to approximate the ...
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### Creating nearest neighbors Laplacian matrix

I want to create a general formula for an $N \times N$ nearest neighbors Laplacian matrix such that I can write an mfile in MATLAB to compute the matrix for given $N$. The nearest neighbors Laplacian ...
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### Least-squares problem with quadratic equality constraint

I want to find the solution of a Lagrange equation whose inputs are matrices. First I have the equation Ax=0. By decomposing $A$ into $A_3$ (columns 9 to 11 of A), $A_9$ (the rest of the columns), ...
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### type of the noise: PDF+Hypothesis test

I have a 2D matrix of values. I've considered these values as a noise. What I'm trying to do is to draw the PDF of my matrix and see the distribution of my data. But it is not enough to say that ...
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### Hurst exponent Algorithm not well defined? What to do in this case?

The R/S algorithm is well known for finding the Hurst component of a given data set. I have one query about whether it is well defined? Suppose in a given partition, all of the values were equal to ...
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### Ball motion with air resistance coupled differential equation for fourth-order Runge-Kutta

I've created a MATLAB function for solving coupled differential equation with the fourth-order Runge-Kutta method based on what is provided here (Simultaneous Equations of First Order). Here the ...
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### How to expand the matrix in Matlab (forming $A$ matrix in least square problem)

If I have 5 data points (actually, this could be vary huge number): $a = [1;2;3;4;5]$ To each data point, I can form a matrix $[a(i),2a(i)]$. (actually, I have to find the matrix, this matrix needs ...
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### The difference between awgn(x,snr) and awgn(x,snr,'measured')?

I use awgn function to add noise to my signal modulation to calculate BER. But when using awgn(x,snr), it make the result wrong, but true with awgn(x,snr,'measured'). I read on mathwork, they said ...
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### Why equals the z-Transform $c^n * u(-n-1)$? according to Matlab/WolframAlpha?

$x[n] = c^n * u[-n-1]$ Where u[n] is Heaviside step function. According to Matlab and WolframAlpha this equals 0. However if I compute the sum according to the z-Transform definition I got (sum from ...
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### Covariance matrix - wrong results either in Matlab or in formula?

The definition of a covariance for discrete variables (taken from https://en.wikipedia.org/wiki/Covariance) is: $$\operatorname{cov} (X,Y)=\frac{1}{n}\sum_\limits{i=1}^n (x_i-E(X))(y_i-E(Y))$$ ...
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### Find a Weight Function with specific characteristics

I need to build a weight function and I want to understand how you would do that. The reasoning you would use to define it. My function has to be something like: $f(\alpha)$ which is: $0$ if \$\...
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### Display the quotient between the value of an histograms

i'm triying to display the quotient of two histograms which have the same borders. Is it possible to do is with Matlab ? Thanks a lot !
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### Matlab sum is wrong: Double symsum gives incorrect result

I'm trying to calculate the double sum $$\frac{1}{10} \sum_{x=1}^{10} \left( \frac{1}{x} \sum_{n=0}^{floor(log_{10}x)} 10^n \right).$$ In MATLAB, my result is ...
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### Match harmonics while decoding the speech signal

There is a matlab's program. In the input parameters is a wav file. After executing a program there are appearing an array of frames. Frames partially recover each other. In each frame there are ...
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### is it possible to generate random ill-conditioned sparse matrix in MATLAB?

I know how to generate ill-conditioned dense matrices (use 'gallery'). I do not know how to generate ill-conditioned sparse matrices. Anyone help?
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### using MATLAB to solve a linear program

Hello I am very new to MATLAB and having difficulty solving a linear program problem using MATLAB, I tried solving it however I am not sure If i did it correctly Use MATLAB to solve the following ...