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# Johannes Fischer

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63 total contributions since 2017

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Creating 3D surface from binary slice images
Have a look at isosurface

16 dagar ago | 1

Using an index in a loop as a variable in another function
You need to provide it as an additional argument (the same holds for d, g, and h): ... alpha(n+1,j) = alpha(n,j) + h * vel...

ungefär 2 månader ago | 0

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Array indices must be positive integers or logical values.
The first entry in any kind of Matlab vector/array/matrix... is indexed with 1 (and not 0, as for example in C++). That is why y...

Save elements of an array in a byte variable.
% random array of 8 rows with 4 bytes each bin = logical(round(rand(8, 32))); % how many bytes are there in total NoBytes =...

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Selecting specific values from an array based on a defined condition
Th logical expression 0 <= m+d <= 300 is not interpreted by Matlab as you think it is. It rather is interpreted as (0 <= m+d...

How to express coordinate range of an area
You are looking for the colon operator (https://www.mathworks.com/help/matlab/ref/colon.html) x = 1119:1121; y = 392:394;

How to make the binarized image clearer
The problem why your output looks like this is not necessarily to do with the imbinarize function. The problem lies in the way t...

Returning negetive numbesr from text file using regexp
With questions like these it's very helpful to have an example of waht exactly your data looks like. If you know exactly how you...

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Solved

Vector creation
Create a vector using square brackets going from 1 to the given value x in steps on 1. Hint: use increment.

Solved

Doubling elements in a vector
Given the vector A, return B in which all numbers in A are doubling. So for: A = [ 1 5 8 ] then B = [ 1 1 5 ...

Solved

Create a vector
Create a vector from 0 to n by intervals of 2.

Solved

Inner product of two vectors
Find the inner product of two vectors.

Swapping the columns based on matrix even length
Assuming that there is always an even number of columns: matrix = repmat(1:10, [3, 1]); L = size(matrix, 2); ind = [2:2:L...

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How to fuse SPECT and CT images having different matrix sizes?
You can import the data using dicomreadVolume (https://www.mathworks.com/help/images/ref/dicomreadvolume.html) There is an intr...

How can I fit a Gaussian to data that only forms the peak
You should always help your fitting algorithm by setting upper and lower bounds for the parameters. Even more important are star...

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ranking of vector with non-unique elements
So you want to order starting with the highest value? F = [10.1 31.0 20.5 20.5 10.1] [~, ~, rankF] = unique(max(F)-F)

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Standard Deviation of 3D matrix with NaN elements
As described in the doumentation for std, there is a flag on how to deal with 'NaN' values. If you want the standard deviation o...

How to make two numeric field related in GUI?
The 'Callback' property of the uicontrol defines which function to call when you press enter while the edit field is in focus. A...

How to randomize audio files
What kind of randomization do you want? Play all sounds once, before playing a sound twice? randomizedOrder = randperm(80); ...

How to reshape a square matrix diagonally to a vector?
I would start with writing down the subscripts in the order you want to select the elements of the matrix. A=[0 1 0; 1 1 1...

How to assign a different name of a matrix for each iteration?
You could use assignin for that purpose: for j = 1 : size(varargout,2) fn = modalfit(varargout{1,j}, f, fs, 10, 'FreqRange', ...

for loop values of certain output range
Two possible solutions: x = 3; idx = 1; for c = -2:1:2; for q = -2:1:2; g = (c*x)+q*(c+x); % g at this...

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Solved

Alternating sum
Given vector x, calculate the alternating sum y = x(1) - x(2) + x(3) - x(4) + ...

How to save the image WITHOUT the white background using imwrite (advanced problem)
% read image as NxMx3 rgb matrix RGB = imread('bird1.png'); imshow(RGB) s = size(RGB); rectangle('position',[1 1 s(2) s(1)...

How do I check if a folder exists which has a variable name?
Your code is trying to store in fname the content of the field 'bin' of the struct 'Measurement_20190829_18_15_10', which propab...

How to find the previous position in an array where a value is met?
This is an ideal playgrouond to see how you can increase speed by avoiding for loops. % My idea is to create an array, that in ...

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Project data for each pixel along the edge direction
Do you know the angle? You could rotate the image to align the edge with the grid and then project along one dimension: %% exam...

Solved

Bullseye Matrix
Given n (always odd), return output a that has concentric rings of the numbers 1 through (n+1)/2 around the center point. Exampl...

Solved

Return the largest number that is adjacent to a zero
This example comes from Steve Eddins' blog: <http://blogs.mathworks.com/steve/2009/05/27/learning-lessons-from-a-one-liner/ Lear...