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

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

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

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...

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...

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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...

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

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

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

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...

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

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

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...

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