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Michael


33 total contributions since 2012

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Question


"text" handle, how do I grab all text and rotate it in a figure?
Hi, I've created a figure and annotated it using "text(x,y,'sample)" code, and I've got about 8 instances of it on my figure....

8 years ago | 1 answer | 3

1

answer

Question


Fastest way to compute spectral norm of a matrix?
Hello I can't find any mention of the spectral norm in the documentation. I want to calculate max(|Ax|)/x for any vector x...

8 years ago | 1 answer | 0

1

answer

Question


colorbar scientific notation exponent won't go away
Hi I've got a square matrix and I'm using imshow and colorbar to plot it. The values are small, so colorbar naturally uses x1...

8 years ago | 0 answers | 1

0

answers

Answered
i've an gray scale image I to be decomposed...i want to extract the low frequency and high frequency component out of it...can anybody help me?
I don't know what LL1 or HH1 are but the 2D discrete Fourier transform should find you the frequency components of the image, in...

8 years ago | 0

Answered
How to plot 3D contours of temperature, on the 3D surface of the body !?
My own suggestion might be to generate the 3D surface using g = surf(x), remove the edges using set(g,'EdgeColor','none'), and t...

8 years ago | 1

Question


MATLAB automatically chose colours for my plot, how do I get them?
ydata is 70x5 xdata is 70x1 plot(xdata, ydata) generates five lines with different colours how do I find what these colou...

8 years ago | 1 answer | 0

1

answer

Question


best way to plot error bars for multiple data?
Hi I have five pairs of curves to plot on a 2d graph. This, I can just about manage- I use five colours and then distinguish ...

8 years ago | 0 answers | 0

0

answers

Question


how to assign a variable using a string
I have a set of variables called "error1", "error2", etc. Each is a 4D matrix and I want to extract certain parts of them for...

8 years ago | 2 answers | 0

2

answers

Question


use of cell arrays to store matrices... but parfor gives an error
Hi, I've got a loop which creates three matrices, and I want to store these for each iteration. Previously I've been saving t...

8 years ago | 1 answer | 2

1

answer

Question


what is the mathematical notation equivalent to abs(A) for matrix A?
I'm trying to write notes for my code and I want to know if there's a common notation which means what abs(A) does, ie. multiply...

8 years ago | 2 answers | 0

2

answers

Question


preallocating sparse 4d matrix
Hi I've got some code that preallocates some matrix L = zeros(50,50,50,50); and then iterates along the first two dimensions ...

8 years ago | 2 answers | 0

2

answers

Question


why does parfor execute loops in a random order?
I can't see any reason why, and if my PC crashes during a 20,000 loop iteration, it's a pain to figure out which iterations are ...

8 years ago | 1 answer | 0

1

answer

Question


"print" saves image with tiny title/xlabel
Hi I'm trying to save a figure using 'print' but this process doesn't preserve the image/text proportions that are on my scre...

8 years ago | 2 answers | 0

2

answers

Question


imresize is blurring my image!
Hello I have a 128x128 matrix and I want to scale it down to 32x32. MATLAB's algorithm "imresize" seems to involve a smoothin...

8 years ago | 1 answer | 0

1

answer

Question


setting processor affinity for individual parallel toolbox workers
Hi Just wondering does anyone know if there are any general rules for improving speed by setting processor affinity using the...

8 years ago | 0 answers | 0

0

answers

Question


Matlab loop (with load/save) is getting slower and slower
Hi I'm running a large code that is basically: for i = 1:50 load(i.mat, input); output = myfun(input); ...

8 years ago | 3 answers | 0

3

answers

Question


Want to change the range of a single axis of a plotyy figure
Hi I want my x-axis to be tight to the data on a plotyy graph. I can't seem to do it without messing up the axes. My data ...

8 years ago | 2 answers | 0

2

answers

Question


Does logical indexing have a direct inverse?
Say I have some region-of-interest filter X, and I use B = A(X~=0) to only extract the values of A where X~=0, is it then possib...

8 years ago | 4 answers | 1

4

answers

Question


How to stop recurring error message if Ctrl+C doesn't work!? (help!!!)
Hi I tried to surf plot a discrete Laplacian matrix operator and it has broken MATLAB... I managed to close the figure, but t...

8 years ago | 2 answers | 0

2

answers

Question


Stopping fmincon based on timer
Hi, I asked this before and accepted an answer before having some trouble implementing the code, so I think I need to ask again....

8 years ago | 3 answers | 1

3

answers

Question


Can I impose a time limit on fmincon without editing the m-file?
I'm trying to compare different algorithms by imposing a time limit, however one of my algorithms calls fmincon and it seems imp...

8 years ago | 1 answer | 0

1

answer

Question


fmincon displays huge unwanted output text
Hi. Does anyone know why fmincon would ignore a 'Display','off' setting in the options? Here is my code: opt = optimset('Ma...

8 years ago | 1 answer | 0

1

answer

Answered
Non linear curve fitting by changing parameters
What is the blue curve? Usually a curve fitter algorithm requires a model (your h function) with specified parameter space (your...

8 years ago | 0

Question


How to reshape a 16x16x16x16 matrix to 256x256 whilst maintaining consistency
Hi I have a pixel grid (16,16) and I've generated a matrix A whose (i,j,k,l)th element specifies a property of the pairing of...

8 years ago | 1 answer | 0

1

answer

Question


How to quantify the spread/separation of points on a circle
Hi, this may be a little vague I have a set of points in the unit circle and I want to quantify their separation, for example...

8 years ago | 1 answer | 0

1

answer

Question


lsqcurvefit.m ... how to find intermediate steps?
Hi I'm fitting using lsqcurvefit and the OUTPUT structure tells me there are 4 steps with 20 function evaluations before the ...

8 years ago | 2 answers | 0

2

answers

Answered
Radon Transform
If the ellipse has a uniform value the integral becomes the product between that value and the length of each beam through the e...

9 years ago | 1

Question


apply filter to a *circular* image
hello I'm trying to filter a circular image, the circle fits inside a square matrix, so for a 100x100 matrix the radius is 50...

9 years ago | 1 answer | 0

1

answer

Question


Multiplying certain dimensions of two 3D matrices
Hi I've got two matrices, one 30x30x50 and one 30x30x80 I would like to multiply them in such a way that the result is a 5...

9 years ago | 3 answers | 0

3

answers

Answered
merging column vectors from the loop in to a single matrix
Try something like: matrix = zeros(rows, columns); % preallocate your matrix for i = 1:columns column = [your code he...

9 years ago | 1

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