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Matz Johansson Bergström
Chalmers University of Technology
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Check out my website: www.matzjb.se for tips on various coding-related problems. Professional Interests: image processing, algorithms, computer graphics, high performance computing.
統計
Feeds
reason for converting image into double
The reason is precision. Say you read an image using (write this in the Matlab prompt) >>Im = imread('filename'); >>clas...
9年弱 前 | 1
why slow 5 times when tic or toc and expression in one line?
Funny enough I also get horrible timings. I am using Matlab 2014a and I get: Elapsed time is 1.053381 seconds. Elapsed t...
9年以上 前 | 0
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How can I fill a matrix column with dta coming from another matrix according to index
Without knowing the size of the matrix, it might be a good idea to use a sparse matrix, instead of filling the non existant elem...
9年以上 前 | 1
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Permutation of array elements
This seems to work A = {'test a 1', 'test a 2'}; B = {'test b 1', 'test b 2'}; WAKE = [A',B'] %see below for explanat...
9年以上 前 | 0
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How to perform skull stripping using matlab?
I found something that might be of help: <http://se.mathworks.com/help/matlab/visualize/exploring-volumes-with-slice-planes.htm...
9年以上 前 | 1
using mex -setup error
As the error message says you are missing a suitable compiler to create mex files. See <http://se.mathworks.com/help/matlab/matl...
9年以上 前 | 0
How can I insert row into matrix without deleting its values?
The only way I know of is to create a new matrix consisting of A and the row and then append the three matrices together, for in...
9年以上 前 | 18
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How to solve the problem Ax=b, when A is (14400,14400) and b (14400,1)?
If A is full \ has to perform a Gaussian elimination. A is ~1.5GB in double precision and it seems that \ requires at least that...
9年以上 前 | 0
I was record on my phone a sound. how to hear that sound in matlab.
I found a matlab script (with exe and library) that can import m4a files. I tried it and it seems to work. See <http://www.ee.co...
9年以上 前 | 0
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how can obtain min of matrix
This solution is maybe a little ugly, but it works Say that A is the matrix. tmp = A; %we will destroy elements, ...
9年以上 前 | 0
How to solve this equation?
This is actually very simple using the *\* operator, see <http://se.mathworks.com/help/matlab/ref/mldivide.html mldivide,\ docum...
9年以上 前 | 0
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Multi-Line Colors in 2014
That's odd. I'm using Matlab R2014a and it seems to be working fine. Are you using Matlab R2014b?
9年以上 前 | 1
what is the difference between a vector and a matrix?
A matrix is simply a rectangular array of numbers and a vector is a row (or column) of a matrix. Read more about the practica...
9年以上 前 | 3
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How can I get different 2D Matrices from a 3D matrix?
The size of the A(1,:,:) will be a 1-by-n-by-z matrix, so you have to temporarily store it in a 2d matrix tmp(:,:) = A(1,:,...
9年以上 前 | 0
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how to crop an image
In my answer I throw away the green and blue channels of the PNG, because it is black/white. If you want to use a color image, t...
9年以上 前 | 2
How to read data one by one
It should be sufficient to write filename='coordinates.txt'; [x,y,z] = dataread('file', filename, '%f%f%f', 'del...
9年以上 前 | 0
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FFT manual help formulation
The range 1:50 is only used in the plot, not in the rest of the example. See <http://se.mathworks.com/help/matlab/ref/fft.html ...
9年以上 前 | 0
Replacing non-alphabetic characters with numbers?
Yet another answer, just for the "cellfun" of it ;-) tmp = cellfun(@(x) isstrprop(x, 'alpha'), {TS1}, 'UniformOutput', fals...
9年以上 前 | 0
how can i read hdr file?
Have you tried http://www.mathworks.se/help/images/ref/hdrread.html?
10年弱 前 | 0
Assigning colors on a cylinder
Simplest way [x,y,z] = cylinder; surface(x,y,z, 'FaceColor','texturemap',... 'EdgeColor','none','Cdata', rand(10)...
10年弱 前 | 1
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How to find first ten prime numbers that are greater than 4?
You could do it like this x = primes(100); %pick primes smaller than, say 100 x = x(x>4); %pick the ones larger than 4 ...
10年弱 前 | 0
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Why aren't my cases working correctly
I would put period and t calculation outside of the switch and I think you want t = linspace(0,period*cycles,100);
10年弱 前 | 0
Index through datestring, selecting whole hours
Another alternative where I just pick the last two characters from the first column of the cell: %mock data: cel{1,1...
10年弱 前 | 0
How can I improve Matlab perfomance for this code?
It seems to me that combntns (which is the same as nchoosek) is taking a long time to finish. So, the appending of the combinati...
約10年 前 | 0
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how to integrate inside 'for' loop
To solve this problem you can use a anonymous function handle to a function with x and n as arguments. f = @(x) myfun(x, ...
約10年 前 | 0
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Plotting a 3D matrix graph
First, I assume that the graph is undirected, edges are going both ways, but you might want to change that maybe. A =...
約10年 前 | 0
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access values in dataset
LinearModel is using tables, so you can write tmp = table2array(Im.Coefficients) and access tmp.
約10年 前 | 0
Color code with dash line
x=1:10; plot(x, cos(x), ':','color',[0,0.5,0],'linewidth',3)
約10年 前 | 2
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what does c(:).' mean? c should be a vector
By writing c(:)' you are making sure that the vector has the dimension 1xn, where n is the length of the vector, a row vector. H...
約10年 前 | 1
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how to create 200 random matrices using loop..
I have not tried it but something like this: n=200; tmp = rand(32,32,n); and then to multiply each matrix for i...
約10年 前 | 0