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Walter Roberson


42,181 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
How to make a matrix with negative indexes?
Modify https://www.mathworks.com/matlabcentral/fileexchange/33301-zero-based-indexable-arrays-oop-exercise Another approach is...

28 minutes ago | 0

Answered
How I can repeatedly divide a binary image ?
Code for repeatedly dividing was provided at https://www.mathworks.com/matlabcentral/answers/456856-how-can-i-loop-over-a-binary...

38 minutes ago | 0

Answered
how i can save the value of two signals when they are equal
N = 14; a = zeros(1, N); b = 1; for K = 1 : length(signal_1) if signal_1(K) == signal_2(K) a(b) = signal_1(K); ...

1 hour ago | 0

Answered
Adding multiple fields and values to structure array
Provided you are setting all of the fields of data(k), then you can use data(k) = struct('PairNum', pairNum, 'level', level, 't...

1 hour ago | 1

| accepted

Answered
How does Matrix(3002:2001:1999998)=0.4 works?
It is due to linear indexing. Variables can be indexed by a single number which is the number of elements from the beginning in ...

2 hours ago | 0

Answered
How can I append the same variables on mat file?
After you have created m = matfile() then new_row_of_values = something appropriate; s = size(m, 'my_variables'); m.my_vari...

2 hours ago | 1

Answered
Recursive computation using multi gpus
No. Within any one process, in order to send commands to a different GPU, you need to select the GPU. Selecting a GPU synchroni...

4 hours ago | 0

Answered
How to create a sliding window??
Apply regionprops() to find the bounding boxes. Sort the bounding boxes by lower left corner, according to x within y (that is, ...

5 hours ago | 0

Answered
How to use sliding window technique to detect one single line
Use nlfilter() to apply nonlinear algorithms to sliding windows. That said, there are some algorithms that can be much more eff...

5 hours ago | 0

Answered
how can I compute memory usage?
You can turn on memory profiling; https://www.mathworks.com/matlabcentral/answers/214247-allocated-freed-self-memory-and-peak-me...

5 hours ago | 0

Answered
ismember 0×0 empty logical array to logic
The obvious answer would seem to be to test if isempty(A) || ~ismember(A,ID) If you were hoping there were a hidden preferenc...

7 hours ago | 0

Answered
How do I write this equation in Matlab?
There is a trick to solving inequalities: convert them to equalities. P/R < 1 implies P < R implies P + dP == R for some posit...

7 hours ago | 0

Answered
how can we create database with .mat files ?
Yes, it is possible. It is, however, of low value to do so. .mat files are just files, so they can be read in as arrays of uint...

8 hours ago | 0

Answered
how to make two differnt size array into same
[T3, ia, ib] = intersect(T1, T2); T3Temp = Temp(ia); T3RH = RH(ib); yyaxis left plot(T3, T3RH); yyaxis right plot(T3, R3Te...

8 hours ago | 1

| accepted

Answered
Incidence matrix of a graph
If you have constructed a graph() object named G, then full(G.adjacency)

10 hours ago | 0

Answered
How can I create a loop that doesnt allow the same number to be input twice?
if length(unique(M)) ~= numel(M) error('You entered some number twice') end

11 hours ago | 0

Answered
[student] Asking your help to solve an issue with a function creating algebric loop
The problem is not that block: the problem is that you have blocks in which the output is connected to the input, but the calcul...

11 hours ago | 1

Answered
One instance running issue
Each run of the compiled executable is a separate process. The global variable will be destroyed between runs, same as if you ha...

14 hours ago | 0

Answered
how to prevent reordering of terms by symbolic math functions
Yes, there is a way. You can create a whole bunch of MuPAD code to use the general framework of the internal symbolic engine in ...

14 hours ago | 0

Answered
What license would cover the following application: making public videos/live streaming tutorials regarding Matlab/Simulink
Student licences only cover MATLAB use for courses and degree requirements. Home license could potentially cover what you des...

16 hours ago | 0

Answered
How can I average datetimes of my array?
Not array2timetable. Use table2timetable

18 hours ago | 0

Answered
Calculating eigenvalues of matrices of symbolic matrices
The symbolic toolbox always considers a resolved symbolic variable to be a scalar, never as a stand-in for a matrix. You would h...

19 hours ago | 0

Answered
For loop count question
a1 = -70:5:100; a2 = -60:5:60; a3 = -50:10:50; a4 = -40:10:40; N_a1 = length(a1); N_a2 = length(a2); N_a3 = length(a3); N...

1 day ago | 0

| accepted

Answered
How can I integrate this function?
planckint = integral(plankck2, 0, 5780, 'ArrayValued', true);

1 day ago | 0

Answered
Undefined function or variable 'x'.
You define theta as a vector. Then you call ode45, which will not change theta. Then you test if theta < 0.7854. With theta bein...

1 day ago | 0

Answered
please how can i plot this excel data in matab in such a way that the time shows in the x axis
t = readtable('weather data matlab.xlsx'); d = days(t.Time); d.Format = 'hh:mm'; C = t.Temp__C_; plot(d, C);

1 day ago | 0

Answered
Sum of a 4D matrix
See https://www.mathworks.com/matlabcentral/fileexchange/9700-random-vectors-with-fixed-sum

1 day ago | 0

Answered
Help with Grid search using parallel computation (substituting for loops using 'parfor')
Effectively, you are trying to do a min() reduction. Unfortunately, min reductions are not supported even if you called min() di...

1 day ago | 1

| accepted

Answered
How fmincon shifts x0 when it does not strictly satisfy the upper and lower bounds?
For activeSet, sqp, and sqpLegacy: Any x0 value that is less than the lower bound for that entry, is replaced with the lower bo...

1 day ago | 0

Answered
Representing fractions in single-precision floating point
I cannot tell at the moment whether you are using Windows or Linux. Either way, sprintf and fprintf truncate the output of value...

1 day ago | 0

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