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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

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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

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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

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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

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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

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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