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Walter Roberson


Last seen: Today
48,558 total contributions 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.

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Answered
Invalid indexing or function definition
I suspect that you accidentally created a variable named solve

1 hour ago | 0

Answered
accumarray works with made up data, but not real data
OT = unique(matA(:, 1)); That will have length equal to the number of unique values OT = [OT, accumarray(matA(:,1), mat...

1 hour ago | 0

| accepted

Answered
Unable to perform assignment because the size of the left side is 3-by-1 and the size of the right side is 4-by-1. X(:,1)=Xint is showing the error
you have an existing variable named X that is interfering with your code

1 hour ago | 0

Answered
Calculating inverse of non square matrix
u1i = u1.'./ sqrt(sum(u1.^2)) could be said to be the inverse, in that u1 * u1i = 1 if I have worked things correctly and ...

9 hours ago | 0

Answered
About the scatter plot.
a = a(:,[2:end,1]) ; and scatter(X(Y==1,1), X(Y==1,2), '*g') scatter(X(Y==0,1), X(Y==0,2), '*r')

10 hours ago | 0

Answered
code of Euler's
@(t,p)0.0169*t

10 hours ago | 0

Answered
Calling different anonymous functions from a for loop
q_array = {@(x)ones(size(x)); @(x) abs(x); @(x) x.^2; @(x) (1/3)+(2/3)*x.^2} ; Now you can q_array{i}(nu(j)) Howeve...

11 hours ago | 0

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Answered
Undefined variable "dsp" or class
You need to license and install DSP System Toolbox; https://www.mathworks.com/products/dsp-system.html

12 hours ago | 0

Answered
Is it possible to install and run MATLAB R2020b on NVIDIA Xavier platform?
You are right, at present MATLAB is only supported on Intel platforms. Next month (December 2020), Mathworks intends to release...

12 hours ago | 0

Answered
Unable to perform assignment because the left and right sides have a different number of elements.
When you enter 7 then the code expects to read 7 lines with 8 values per line (though as the prompts hint you can put as many va...

16 hours ago | 0

Answered
Creating a symbolic array
a = sym([]); or better yet a = zeros(5,5,'sym')

17 hours ago | 0

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Answered
Need help in viewing a 2D image in 3D space.
volumeviewer perhaps. But I suspect idx = find(YourMatrix) ; [r, c, p] = ind2sub(size(YourMatrix), idx); scatter3(c, ...

22 hours ago | 0

Answered
How to write if statement for logical value
any(Result{1,1}, 1)

22 hours ago | 0

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Answered
GA does not solve problems with integer and equality constraints.
you can still use ga but you have to tell ga that you have no integer constraints. Then you have to provide a population functio...

22 hours ago | 1

Answered
Error using sym/subsindex () while using the symsum function
You can never use an unresolved symbolic variable as a subscript. You must always use definite numeric or logical values for ...

22 hours ago | 0

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Answered
Error in Cumtrapz?
Remember after one integration you get a formula with a constant of integration, and when you integrate that, you get the double...

1 day ago | 0

Answered
How to remove duplicates from a matrix without using unique?
[~, a]=findgroups(d);

2 days ago | 1

Answered
or() in categorical variable
ismember(financial_status, 1:2) At the moment I cannot think of any computer language that expresses a set membership test ...

2 days ago | 0

Answered
can matlab calculate the area of irregular shape base on 2D-grid ?
No, in the general case the area of irregular shaped objects is not defined. See https://en.m.wikipedia.org/wiki/Koch_snowflake ...

3 days ago | 0

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Answered
Resizing the images to 100 x 100
TestData.Files(1:20) = cellfun(@(I) imresize(I,[100,100]), TestData.Files(1:20), 'uniform', 0); The code would have been sh...

3 days ago | 0

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Answered
how does sum work?
you have one / operator that should be ./

3 days ago | 0

Answered
GA Toolbox maximization fucntion
To maximize a function, minimize the negative of the function @(x) -f(x)

4 days ago | 1

| accepted

Answered
можно ли сделать так, что бы сетка отображалась поверх 3D графиков?
fig = figure(); ax1 = axes('Parent', fig); [X, Y] = meshgrid(1:50, 1:60); Z = X.^2 + Y.^2 - cos(X.*Y); surf(ax1, X, Y, Z, ...

4 days ago | 0

| accepted

Answered
how to compand the complex valued signal
https://www.mathworks.com/help/comm/ref/compand.html#fp1068641 Look in the Algorithms section, which gives the formulas. Thos...

4 days ago | 0

Answered
Plot of an equation of three unknown variables
http://www.mathworks.com/help/matlab/ref/slice.html http://www.mathworks.com/help/matlab/ref/isosurface.html For a full plot o...

5 days ago | 0

Answered
what does this line do
The code goes through all of the F cell entries, and finds the number of columns in each, recording the number of columns in num...

5 days ago | 0

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Answered
Coding an equation (with summation within equation) with nested for Loops
You are probably summing T_xt(:,:,:) over the third dimension to get T(x,t) . However, when you do that, you would be adding T_...

5 days ago | 0

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Answered
Matlab solver for natural log equation
Q = @sym; %convert to rational syms x eqn = log(Q(0.5)) == (-Q(27109)/x)-Q(0.95)*log(x)+Q(25.18) S = solve(eqn,x) vpa(S) ...

5 days ago | 0

Answered
How to use parfor instead of for in this function
That is not possible. The output when i=2 depends on y(:,2) having been set properly, but y(:,) has not been assigned to until i...

5 days ago | 0

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