Questions tagged [gaussian]

For issues related to any of the uses of the Gaussian function. Don't forget to add additional tags to clarify the context.

The graph of a Gaussian is a characteristic symmetric "bell curve" shape that quickly falls off towards plus/minus infinity. The 1-D Gaussian is defined as (taken from wikipedia):

gaussian function from wikipedia

The parameter a is the height of the curve's peak, b is the position of the centre of the peak, and c controls the width of the "bell".

In multiple dimensions, the Gaussian is defined as the product of 1D curves along each dimension.

Gaussian functions are widely used in statistics where they describe the normal distributions, in signal processing where they serve to define Gaussian filters, in image processing where two-dimensional Gaussians are used for Gaussian blurs, in mathematics and physics where they are used to solve heat equations and diffusion equations, to formulate the propagation of optical beams (Gaussian beams), to from a basis set of wavefunctions, to define the Weierstrass transform, and many more.

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Method for initial guess of standard deviation of 2d gaussian/gabor?

I'm working on curve fitting software in Matlab. So far it's going pretty well but I need a method of inputting an initial guess for my curve fitting software. I'm given a selection of points, but I need to find an initial guess of the SDx and SDy…
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UIImage Gaussian Blur with vImage

I am trying to find a faster way to generate Gaussian Blur image, this blog works great with most of the image. But when image has transparent backgroudcolor, the blured image looks bad The code below is copied from the blog: -(UIImage…
Shawn Wang
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How to change an image to gaussian blur?

The four transformations you should implement all compute the new pixel values as a weighted average of the old ones. The only difference between them is the actual weights that are used. You should be able to add a single method inside class…
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Matlab: plot 2 and 4 3d gaussians on same axes

With this code: x=linspace(-3,3,25); y=x'; [X,Y]=meshgrid(x,y); z=exp(-(X.^2+Y.^2)/2); h=surf(x,y,z);shading interp %colormap(col4); set(h,'LineStyle', '-','LineWidth',0.001,'EdgeColor','k'); set(gca,…
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Detecting circles in an image using laplacian

I'm trying detect the disk and cup in the back of an eye (fundus) to calculate certain things later on. So here is an image of the eye: I'm just trying to detect the disk, or the larger yellow-ish circle on the right side of the image, and the cup,…
Shalin Shah
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How to create noise for a 2D Gaussian?

I'm trying to practice curve fitting on a 2D Gaussian, but in order to do that I need to add random noise to my predefined Gaussian. My first instinct was to cycle through two for loops and create two matrices X and Y with random numbers, but when I…
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How to create 2D data set from Gaussian distribution in R?

I need to create "2D data set with 200 samples created from a multivariate Gaussian distribution with a non-diagonal covariance matrix", but I'm neither a statistician nor a mathematician, and I didn't exactly get this. Here is what I understood.…
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Fitting a mixture of gaussians with negative weights

I know Gaussian Mixture Models are used for distribution of points and thus the functions they represent are positive (PDFs are postivie). However I want to approximate a function using GMMs which could also be negative. Is there any way to…
Ameer Jewdaki
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Conditioning Gaussian process regression

I was wondering how I could condition a Gaussian process (e.g., by adjusting a covariance function?) to produce only those trajectories that meet some pre-set constraints. As an example, the following code written in R produces smooth curves…
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Convert browser blur pixel value to ImageProcessor Library GaussianBlur kernel equivalent

im tring to write a image editor which you can edit the image on the client and make the changes on the server (lite version of paint). it does filtering, crop resize and ... problem: imagine i choose 10px of blurness in my editor, when i pass the…
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Mixture of 1D Gaussians fit to data in Matlab / Python

I have a discrete curve y=f(x). I know the locations and amplitudes of peaks. I want to approximate the curve by fitting a gaussian at each peak. How should I go about finding the optimized gaussian parameters ? I would like to know if there is any…
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Is there any GMM (gaussian mixture model) background subtraction implementation for pcl (pointcloud)?

I want to know if there is any implementation of GMM (Gaussian Mixture Model) for PCL library? Actually I have searched but I couldn't find any library or source code! The main idea is using this GMM technique to detect moving object's point cloud…
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Peak detection gives different results when using octave or oct2py in python

I am trying to fit a number of fixed width gaussians to a single broad peak. The only way I have been able to do this is with peakfit.m. Sample data can be downloaded here. In octave the code I use…
Peaksandpeaks
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Clustering algorithms for machine learning sample

I have a 1830*6800 matrix like below: The row 1830 is for different startup companies ID, the column is for 6800 different investors. Now I want to find the similarities between those companies that successfully collect enough money, and those who…
Tom Dawn
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How to estimate a Gaussian mixture model with the EM algorithm in SAS?

I am trying to fit a univariate Gaussian Mixture Model with the EM algorithm. But I only found a package in R (mclust). Does anybody know an equivalent proc step in SAS 9.3?
Da_Stat
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