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Bruno Luong


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1.106 total contributions since 2009

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Answered
interpn vs griddata: how are results different?
Mathematical, in short the difference is INTERPN uses tensorial linear function on nd-hypercube that enclose the query point. ...

alrededor de 13 horas ago | 0

Answered
Usage of structure as input of a function. Is it efficient ?
"I've struggled to find ressources online about that matter (maybe I didn't find the right keywords" No, it's not your fault, T...

alrededor de 16 horas ago | 0

Answered
Find/return value from each row in a big matrix that corresponds with a condition/value
"Let me specify, I only want the first time the value appears in each row and if the value dont appear I want closest value." T...

alrededor de 18 horas ago | 0

Answered
Convert subscripts to linear indices with dynamic matrix size
% Generate random array of nd-indexes sz=[3 4 5 6]; m = 10; n = length(sz); SUBIDX=ceil(sz.*rand(m,n)); % Method 1, with ...

alrededor de 19 horas ago | 1

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Answered
Vectorize a code involving multiple loops commands
x = [0:0.1:10]; a=[2 1; 0.5 0.25]; b=[500 200; 300 250]; c=[0.25 0.35; 0.15 0.25]; d=[0.5]; X = reshape(x,1,1,[]); AB = ...

alrededor de 22 horas ago | 1

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Answered
Conditional Random number generation
m = 5; n = 3; s = 10; This will generate uniform distribution with sum criteria % generate non-negative integer random (m x ...

1 día ago | 0

Answered
Rounded random numbers with fixed sum
k = 3; r = (diff([0 sort(randperm(100+k-1,k-1)) 100+k])-1)/100

1 día ago | 0

Answered
mex-file crashes MATLAB in for loop
Those are wrong, you should not Free the pointers that you are not Malloc. mxFree(a_double); mxFree(b_double); mxFree(z_do...

1 día ago | 1

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Answered
C = union( A,B ) is too slow. Is there any faster way given that A and B are ordered.
If you have a decend C-compiler you might use my MEX MERGE SORTED ARRAY c = mergesa(a,b); % or mergemex(a,b); c = c([true; dif...

1 día ago | 1

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Answered
Recover matrix Z from XZX', Z es symmetric and n-by-n, while X is k-by-n where n>>k
You can't getback to 27x27 covariance matrix Z after reducing it it on 5 dimensional space (by X). The information lost forevver...

2 días ago | 0

Answered
solve A*X=B containing very large or small elements
Work with unitless system, scale your matrix, or use automatic scaling if you don't want to bother.

2 días ago | 0

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Answered
How do I shift columns (left or right) in a matrix
k > 0 shift right k < 0 shift left A*diag(ones(1,size(A,2)-abs(k)),k)

2 días ago | 0

Answered
How to solve the equation of binary logic operation, where all unknowns are 0 or 1
[x1,x2,x3,x4,x5,x6]=ndgrid(0:1); x1 = x1(:); x2 = x2(:); x3 = x3(:); x4 = x4(:); x5 = x5(:); x6 = x6(:); b = [x1+x2+x3+...

3 días ago | 0

Answered
Finding the most orthogonal set of n vectors from dataset of unit vectors
I propose this % random test A, which represents 100 normalized vector in R^5 n = 5; m = 100; A = randn(n,m); A = A ./ sqrt...

3 días ago | 0

Answered
EVALIN cannot execute a return?
Yes it is written in the doc. From EVALIN/EVAL document page "evalin(workspace,expression) ... expression — Expression to ev...

4 días ago | 1

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Answered
Matrix compare and unkonw relationships to find
Use regression methods. If you have a linear/affine model, then use linear algebra. If you have "kind" non-linear, use polynomia...

4 días ago | 0

Answered
Why is memory reduced for an identical copy of a sparse array?
Nah nothing to do with name length, it's the number of internal non zeros of ('Ir" and "Pr" old notation) array reserved by MATL...

4 días ago | 1

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Answered
(Block-) Matrix multiplication inaccuracy
Same problem, don't count on exact associativity when working with floating point arithmetics. I can quote word-to-word from wha...

4 días ago | 0

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Answered
Reshape n-th dimension of an array
You operation makes the array changing its size, you can't use for-loop to store the rotated page in the SAME arrray. And btw f...

4 días ago | 1

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Answered
Curl, Divergence calculation from velocity data
Your data is already gridded, no need to gridded on top of it load('matlab.mat') UU=reshape(data(:,3),[75 62]); VV=reshape(...

4 días ago | 0

Answered
Checking a matrix for duplicates in specific row, removing the respective columns
d= [1 2 2 3 4 5 6 6 7; 1 2 3 4 5 6 7 7 8] dd = diff([nan,d(1,:),nan])==0; remove = dd(1:end-1) | dd(2:end) x_cut = uni...

5 días ago | 0

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Answered
Interpolating at vertices of a mesh
In theory you cannot. A function that is piecewise constant on elements is discontinuos at the vertices and you cannot speak ab...

5 días ago | 0

Answered
Obtain the mean angle (circle mean of a file)
angledata_deg is your angle data in degree meanangle_deg = rad2deg(atan2(mean(sind(angledata_deg),2),mean(cosd(angledata_deg),2...

6 días ago | 0

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Answered
How parentheses effects multiplication with pi ?
From wikipedia "While floating-point addition and multiplication are both commutative (a + b = b + a and a × b = b × a), they a...

6 días ago | 0

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Answered
Adding zeros to matrix
% Replace this with your image Image100 = peaks(100)+10; %Centering padding in 4 sides PadImage300 = zeros(300,300,size(Ima...

6 días ago | 0

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Answered
How to create a surface with random spheres protruding?
Is this you want? x = linspace(0,1); y = linspace(0,1); [X,Y] = meshgrid(x,y); Z = zeros(size(X)); N = 30; for k=1:N ...

6 días ago | 0

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Answered
Integral calculation using matlab
Feel free to change these hyper-parameters n = 3 k = 2*pi*rand() integral(@(phi) arrayfun(@(phi) abs(integral(@(theta) exp(...

7 días ago | 0

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Answered
Combining function handles into one function handle
a = @(x) x(1)^2+x(2)^2; b = @(x) x(3)^2-x(4)^2; c = @(x) x(1)*x(4); % suppose your for-loop puts each function handle in a ...

7 días ago | 0

Answered
I cannot find the distance between two matrices with respect to the Frobenius inner product.
Distance in frobenius scalar product: dist_AB = norm(A - B, 'fro') which is the same as this norm(A(:)-B(:),2)

7 días ago | 0

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Answered
Indexing problem with matrices
A = [3 5 9 6 ; 2 1 13 6 ; 6 8 52 4 ; 13 6 8 22 ]; GRID = [linspace(1,100,100); rand(1,100); rand(1,100)]' Code [tf,loc]=ismem...

7 días ago | 0

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