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Walter Roberson


Last seen: Today Active since 2011

I do not do free private consulting. If you want to bring my attention to something, send a link to the MATLAB Answers location. I am currently caught up to T0099119; if you are waiting on a reply from me for an older issue, please send me a reminder.

Programming Languages:
C, MATLAB, Shell, Perl, Fortran
Spoken Languages:
English

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Answered
How to sub sym to a number in a matrix
subs(val, q(1:2), [VALUE1; VALUE2])

5 hours ago | 0

| accepted

Answered
Is there any other function faster than sum(A,2) to get the sum of all rows?
Switching to columns can improve performance as it allows better use of hardware cache.

12 hours ago | 0

Answered
unable to use solve or fsolve for linear system
those cross() calls each return a vector, and you compare the vector to [0 0 0] giving a vector result. You then try to store th...

14 hours ago | 0

Answered
Can we choose step size rule in fmincon?
https://www.mathworks.com/help/optim/ug/optimizing-a-simulation-or-ordinary-differential-equation.html#btfixqo shows some contro...

2 days ago | 0

Answered
How to copy a matrix but skipping some row and column?
M = rand(24, 24); toskip = [1, 2, 4, 6, 8, 17, 19]; %version 1 M1 = M; M1(toskip, :) = []; M1(:, toskip) = []; size(M1) ...

2 days ago | 0

Answered
Matrix is close to singular or badly scaled. Results may be inaccurate.
You have enough duplicate t values that when you calculate "a" the rank does not reach 7; rank of a2*a does not reach 7, so your...

2 days ago | 0

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Answered
How to use use an anonymous function to fit data based on the fittype and fit functions.
There is no chance of fitting that function. fit() and fittype() pass in numeric data, and diff() of numeric data is always sma...

2 days ago | 0

Answered
Speeding up fread for random position in big file
In my experience, you can be more efficient on conversion of 12 bit data than what is done by fread() If memory serves raw = u...

2 days ago | 0

Answered
How can I get this code to work? I am trying to fit the equation that contains step and delta function to experimental data. But I am getting the following error.
Your Energy are in the 500 range. exp(pi*energy) overflows double precision. Your code then divides by large values, but you hav...

2 days ago | 0

Answered
Is it possible to decide which line is variable names in readtable?
Yes, you can do that. For example, variable_row = 3; datatable = readtable(filename, 'VariableNamesRange', variable_row); In ...

2 days ago | 0

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Answered
Double condition to find index
freq = 2000; %hz threshold = 20; %newtons significant_time = 50; %milliseconds significant_samples = ceil(significant_tim...

2 days ago | 1

| accepted

Answered
How to run a .exe file in other computers without Matlab?
https://www.mathworks.com/products/compiler/matlab-runtime.html has links to download mcr 8.5 (R2015a) In https://www.mathworks...

3 days ago | 0

Answered
Solve IVP with Taylor method of order
https://www.mathworks.com/matlabcentral/answers/1746100-whole-derivation-of-two-variable-differential-function#comment_2229660 a...

3 days ago | 0

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Answered
Error in the for loop of my function
The second parameter to symsum must be a scalar symbolic variable that will be summed over. However in your code, the second par...

4 days ago | 0

Answered
How do you create a scatter plot using select columns from app.UITable.Data?
scatter(TableName{:,2}, TableName{:,4})

4 days ago | 0

Answered
Is it possible to get the path of a file using uigetfile() ?
[filename, filepath] = uigetfile(); if ~ischar(filename); return; end %user cancel fullname = fullfile(filepath, filename); ...

4 days ago | 1

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Answered
eeg data to move a motor
Create a numeric array in which each row is a different (fixed-length) eeg sample, and in which you have another variable which ...

4 days ago | 0

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Answered
Extracting Categories from array
As the Tips says, C includes all categories in A, even if A does not contain any data from a category. To see the unique values...

4 days ago | 1

Answered
How can I determine the cluster of pixels in an image that are red or green and quantify how many of the clusters are green or red?
filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/1036195/image.jpeg'; YourRGBImage = imread(filename)...

4 days ago | 0

| accepted

Answered
Why there is an error in line 132? ( [Fit(1,j), tetaDE]=selectmodel2(Pop(:,j),NP,D,mphi,start,nodata,y,u);)
The following fails because you did not provide initbp() ui = [ -3.7287749e-001 1.5462074e-001 3.6396491e-001 -2.254015...

4 days ago | 0

| accepted

Answered
pair-was operation on 3D image(3D matrix)
You need to give up on the algorithm. If you were able to represent the results with one byte each, you would need 3435973836800...

4 days ago | 0

Answered
pair-was operation on 3D image(3D matrix)
findgroups() on the image. You probably are using uint8 so at most 256 different groups. Record the second output of findgroups(...

4 days ago | 0

Answered
Order of operation using ./
The order of operations is always left to right at the same precedence except for obscure behaviour for (^-), (.^-), (^+), (.^+)...

4 days ago | 0

Answered
I want to know how to create dynamic string array
for K = 1 : 5 out(randi(10)) = "entry #" + K; end out

4 days ago | 0

Answered
remove all strings from nested cell array
C = num2cell(randi(9,4,10)); C(randperm(numel(C), 4)) = {"string"}; C(randperm(numel(C), 4)) = {'chars'}; C for K = 1 : ...

4 days ago | 0

Answered
Whole derivation of two variable differential function
The equations are being careless about which variables depend on which variables, and on which variable the differentiation is w...

4 days ago | 0

Answered
Plotting points inside a circle
maxr = 5; %create data N = 20; r = rand(1,N) * maxr; theta = rand(1,N) * 2*pi; [x, y] = pol2cart(theta, r); %plot ...

4 days ago | 0

Answered
Current Directory for Generated Code
MATLAB Coder is designed to target embedded systems, so functionality that is not part of the C Standard Library is often not av...

4 days ago | 0

| accepted

Answered
Variable Number of Arguments
The special keyword is varargin not varagin

5 days ago | 0

Answered
Import part of dataset in a HDF5 file, by 'member' and/or 'logical array'
<https://fossies.org/linux/hdf5/examples/h5_compound.c> The approach seems to be to use the H5T utilities to create a prototy...

5 days ago | 0

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