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# Xin

### ETH

34 total contributions since 2016

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Question

Constrained optimization, free code
Dear all. I have a constrained optimization problem where I used the fmincon function, and it works perfectly well. But it does ...

2 months ago | 1 answer | 0

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Question

Get the middle point of a matrix
Hi everyone. I have an interesting situation. So the idea is to calculate the value of middle points of a 1D, 2D or 3D matrix. ...

10 months ago | 1 answer | 0

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Question

save image without the white border
Hello. I would like to save a phot, or any imagesc, pcolor or whatever 2D image. But the problem is that matlab alway automatica...

1 year ago | 2 answers | 0

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Question

Uncertainty of constrained minimization
Hello everyone. I have a question about the uncertainty of linear minimization. Basically I want to solve for a constrained mini...

2 years ago | 0 answers | 0

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Question

Visualization volume data like pcolor3
Basically I was looking for a pcolor3 like function that can run in newer version of matlab. The idea of using slice to have mul...

2 years ago | 0 answers | 0

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Question

Compute three solution for cube root including imaginary number
Hello everyone. I have a vector composed of some positive and negative numbers. Is there is simple way to quickly get the three ...

3 years ago | 0 answers | 0

### 0

Question

Search for components in symbolic
Hello. Let's say I have a symbolic function: exp(5*x)*x^3. Is it possible to let MATLAB automatically search for the component ...

3 years ago | 1 answer | 0

### 1

Question

2D convolution with 1D output
Hi everyone, basically I need to compute the following convolution problem in 2D, but with only 1 array output. Is it possible t...

3 years ago | 1 answer | 0

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Question

Fast computation of 2D summation
Hello. I have two matrix, A and B and I want to compute the following 2D summation to get a 1D array T. Is it possible to use, e...

3 years ago | 1 answer | 0

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Question

Column vector multiplied to a row vector, memory v.s. speed issue
Hello everyone. I have a column vector (A) that is left multiplied to a row vector (B). The result is a matrix C=A*B. What I nee...

3 years ago | 1 answer | 0

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Question

Set up tolerance and maximal iteration number for lsqlin
Hello, I have a system of linear equations L*X=R and I try to use lsqlin to get the solution with least square. The system of eq...

3 years ago | 1 answer | 0

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Question

Solve linear system of equations with constains
Hello everyone. I have a linear system of equations that make a matrix, L*x=R. x is composed on many variables, e.g. x=[x1 x2 x3...

3 years ago | 1 answer | 1

### 1

Question

Derivative of legendreP function
Hello. I am wondering how could one differentiate the legendre polynomial, e.g. like legendreP(5,x) can be expressed as (63*x^5)...

3 years ago | 1 answer | 0

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Question

Elegantly refer to the second output from a function
Hello everyone. I have a function (matlab function, say "ismember") and I want to use the second output from this function as in...

3 years ago | 4 answers | 1

### 4

Question

Find if a point is inside tetrahedron
Hello everyone. I have a point in 3D space and a FE mesh containing many tetrahedron elements with four corner nodes and the 3D ...

3 years ago | 1 answer | 0

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Question

Delaunay meshing problem with stretched mesh
Hello, everyone. I have a meshing problem using Delaunay function. I have evenly scattered points (stored in x y and z vector) d...

3 years ago | 0 answers | 0

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Question

Compute mean and diff faster
Hello everyone. I am working on a FD code and need to do a lot of averaging in very large 3D/2D matrices. I want to do the follo...

3 years ago | 3 answers | 0

### 3

Question

Convert color to value
Hello everyone. I have a jpg image with blue to red color corresponding to different value. There is also a colorbar showing eac...

3 years ago | 3 answers | 0

### 3

Question

Colorbar design from log negative to positive
I have a 2D matrix and the value vary exponentially between negative to positive. I want to design a colorbar that looks like be...

3 years ago | 0 answers | 0

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Question

I have a GUI that has a static text box which I use to update for the status of the code. The GUI needs to load data from an exc...

3 years ago | 1 answer | 0

### 1

Question

save figure in GUI
I have a GUI with two axes and many other buttons. I would like to save one axis into 'jpg' or 'tif' file. However when I tried ...

3 years ago | 1 answer | 0

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Question

Add element to the matrix in one sentence
I have a 2D matrix, say A=zeros(10,10). I want to add a vector of number to the matrix. I have the index of the elements, but it...

4 years ago | 2 answers | 0

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Question

Indexing 3D matrix with three 1D vector
I have a 3D matrix, say A=100*100*100. I want to index 5 elements from it. What I have are three 1D vector (lenght=10), say x=[1...

4 years ago | 1 answer | 0

### 1

Question

Solve large linear system of equations with klu function
I have a huge sparse function L (10 million*10 million). It is not symmetric. Most off-diagonals are zeros. I want to solve for ...

4 years ago | 0 answers | 0

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Question

Overlap two pcolor with different color and set up transparency

4 years ago | 1 answer | 1

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Question

sample from arbitrary continuous distribution
Say I have a very complicated probability distribution function: x^(-2)*y^(-3)*exp(-z/t), where x y z t are all continuous posit...

4 years ago | 1 answer | 0

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Question

Solve equation with order higher than 32
I have a very high order equation, something like 0=x^50 + a*x^49 + b*x^48 +...+ 1 I tried to use fzero or program Newton Raphs...

4 years ago | 1 answer | 0

### 1

Question

Colormap, how to get the color of the sea
This is an interesting question to me. I wanted to create a nice colormap with very smooth and gradual transition from white to ...

4 years ago | 1 answer | 0

### 1

Question

Generalized nonlinear inverse problem
Anybody knows if there exist a function that applies the so-called Generalized Nonlinear Inverse Theory (Tarantola and Vallette ...

4 years ago | 0 answers | 0

### 0

Question

non linear Least square fitting
I have an equation: z = A*(y^B)*exp(C*x) where x,y,z are my data points, and A B C are the unknowns that I want to fit. ...

4 years ago | 1 answer | 0