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L1 Optimization in matlab
Make some d and F just to test it. d = [1;2;3;4;5]; F = [.1 .3 .5 .7 .9; .2 .4 .6 .8 1.0]; I can think of two ways. ...

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how can we represent the histogram of a vector without using the hist function ?
Is it that you just don't want the bar graph that comes up with HIST? If you call it with output arguments, you can get the valu...

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Taking weighted means over matrices with missing data
M = [4 NaN 1 NaN; 5 3 8 NaN; 1 6 2 4; 8 4 7 2]; w = [0.4 0.3 0.2 0.1]; W = bsxfun(@times,~isnan(M),w); W = bsxfun(@...

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Get rid of nested for loops?
A few observations: 1. A lot of the operations you are doing can me written more efficiently as matrix operations (dot prod...

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How to find zero elements in a three dimensional matrix whose neighbors are all zero.
As you guessed, there are much simpler ways to do it using image processing techniques. % Just making some random data to w...

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Intersection of Two Implicit Curves over a domain
This sort of problem can be solved easily using FSOLVE circ = @(x,y) x^2+y^2-4 elp = @(x,y) ((x-2))^2+((y+2)/4)^2-1 ...

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while loop in matlab password GUI
In your GUI case, the reason it displays 'a' after just one failed attempt is, this loop: username1= 'xxx'; password1= '...

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How to calculate conditional sum of a part of vector/array based on a 2nd one
Just for comparison, here is a FOR loop solution. FOR loops can actually be very fast, even for large arrays, especially when yo...

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Negative gain and phase margin, yet a stable and robust system... can somebody explain?
When I try that, I get something completely different. How are you defining your P and C? s = tf('s'); P= 1.429e-07*1/(s...

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How to create a boxplot from a PDF?
How about something like this. Generate the CDF from your data as Tom suggested, invert it, use the inverted CDF to generate a ...

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Values of intersection points of plot. Print results.
If your x is the output of an ODE solver, then it might not hit x2 = 1 exactly and you will need to interpolate. You could us...

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Large Sparse Matrix Summation
This seems to work well: % Making some random data... N = 1000; K = 100; A = sprand(N*K,N,0.0001); [r,c,val...

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updating a second matrix in specific lines as you loop through a first one
There is also the very useful ACCUMARRAY command: AAA = [ 1 100 102 4 55 58 11 33...

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How to force slope to be zero at a particular point using function PolyFit?
If you have LSQLIN in the Optimization Toolbox, this can be done with a little bit of effort, as described here <http://www.ma...

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how to plot magniture and phase response of a filter?
You need to do elementwise division, use "./" instead of "/" Hw=(0.1*(exp(1j*w)-1))./(exp(1j*w)+0.8);

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Construct a reference to a matrix where the matrix name is the value of a variable
If you need to reference a variable with a dynamic name based on a string, you'd generally call EVAL. That being said, doing the...

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Sparse Matrix - More Efficient Assignment Operation
The performance of sparse matrix indexing was enhanced in R2011a. <http://www.mathworks.com/help/matlab/release-notes.html> ...

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How many times does each number appear?
Assuming that the second column of a is always >= the first column of a, then this is an efficient solution. mA = max(a(:));...

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Performance Issue of 'imrotate' in double precision mode
Hi Dehuan, If you are able to upgrade to a newer version, performance improvements for IMROTATE were implemented in R2012b. M...

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How to average a multidimensional array with surroundings
This would be much simpler if it were not for that weird edge case. Anyways, this is how you would do it in the case of an arbit...

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How to find length of branch in a skeleton image?
You can first find the branch points and endpoints using BWMORPH, and then call BWDISTGEODESIC to get the distance from the bran...

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Flip last 3 bits of vector
You can use BITXOR, V = uint16( round(65535*rand(5,1)) ); V2 = bitxor(V,1+2+4); % 1+2+4 = 7 = 0000000000000111 de...

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Help on for loop
No need to iterate. MATLAB makes this simple with logical indexing. U = [0.0137;0.0081]; R = [0;0;0;72;0;90]; U_f...

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Vectorized Solution to Rotate Multiple Points each at a Different Angle
This vectorized solution uses complex exponentials and works about 2 orders of magnitude faster for large vectors. M = exp(...

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how to filter points which are on a straight line
F = [1 1; 2 2; 3 3; 4 5; 5 5; 6 6; 7 7]; dydx = diff(F(:,2))./diff(F(:,1)); F(1 + find(diff(dydx)==0) ,:) = []

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preallocating sparse 4d matrix
You can't make a sparse array with more than 2 dimensions, but you could make a 100x100 cell array that is filled with 100x100 s...

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Can we run simulink by m file when simulink interface is not opened
Yes, you can use the LOAD_SYSTEM command to load the model into memory without bringing up the Simulink interface, for example: ...

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Matlab: find the contour and straighten a nearly rectangular image
I've done this before: <http://www.mathworks.com/videos/solving-a-sudoku-puzzle-using-a-webcam-68773.html> This is the strat...

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How do I move a cloud of points in 3D so that they are centered along the x-axis?
%% Step 1. Center the data at zero: xyz0=mean(XYZ); A=bsxfun(@minus,XYZ,xyz0); %center the data scatter3(A(:,1),A(:,2...

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Image processing GLCM gray level cooccurance matrix
It's just the default setting. You can change the size by using the 'NumLevels' parameter. For example, I = imread('pou...

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