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Walter Roberson


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47,690 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
Check for hexadecimal number
regexpi(S, '^0X5[A-F][0-9A-F]{2}$') if the result is empty there is no exact match (but it might be a hex number in a diffe...

29 minutes ago | 0

Answered
Failure in initial objective function evaluation. FMINUNC cannot continue. Need some help
When you have the option SpecifyObjectiveGradient, then your function must be able to return the gradient as well as the objecti...

2 hours ago | 1

Answered
How can I install trial version 2016a matlab for 64 bits
You will need to contact Mathworks Sales for custom trials. Mathworks will probably be reluctant to grant a trial for such an o...

2 hours ago | 0

Answered
storing unknown matrices size in a single matrix
Use an array structure similar to class_identifier1 student_id1 class_identifier1 student_id2 class_identifier1 student_id3 ...

3 hours ago | 0

Answered
Save UIFigure as .jpeg or Add Style to UITable with Figure (not UIFigure) Parent?
As of R2020a it is possible to export a uifigure . https://www.mathworks.com/help/matlab/ref/exportapp.html exportapp does no...

3 hours ago | 0

Answered
Computing the outer product (BLAS 2 operation) raised to the power k using the least number of flops
LAPACK and BLAS are designed for computational efficiency, which is not the same thing as reducing the number of FLOPS. The leas...

3 hours ago | 0

Answered
sacar la primera, segunda, tercera y cuarta derivada de una función
You just keep going. After Derivada=diff(f,x,1); you can segunda = diff(Derivada, x); tercera = diff(segunda, x);

6 hours ago | 0

Answered
How to resize array using a mask
a(logical(cell2mat(mask)),:)

6 hours ago | 0

Answered
Student version running on different OS and machine at a time
can I install and run Matlab on the same computer but under different OS? Since this is a dual boot machine, it will be one OS a...

6 hours ago | 0

Answered
Skip specific line from a text file
If you use fopen / textscan / fclose, then you can specify 'commentstyle', 'e r r' . That tells it to skip from 'e r r' to the e...

6 hours ago | 0

Answered
Files missing from a folder
for K = 1 : 2041 thisfile = sprintf('%d.txt', K); if ~exist(thisfile, 'file'); continue; end %file exists, proces...

7 hours ago | 0

Answered
Will Matlab mldivide( \ ) operator use all the available cores when used on multi-node?
It will use up to the current maxNumCompThreads https://www.mathworks.com/help/matlab/ref/maxnumcompthreads.html The number of...

7 hours ago | 0

Answered
surrogateopt: Dot indexing is not supported for variables of this type.
Removing the -nojvm solves the problem (for reasons currently unknown.)

10 hours ago | 1

| accepted

Answered
Numerical integration of symbolic equation
This is impossible to do as a numeric integration.

16 hours ago | 0

Answered
specifying the horizontal linetype '_' produces an error.
https://www.mathworks.com/help/matlab/ref/linespec.html horizontal line style is '-' not '_'

16 hours ago | 0

Answered
Solve Function Doesn't Give The Solutions
Warning: Solutions are parameterized by the symbols: x. To include parameters and conditions in the solution, specify the There...

23 hours ago | 0

Answered
Unrecognized function or variable when reading an excel file.
When you have if expression then MATLAB considers the condition to be true only if all values of the expression are non-zero. Y...

24 hours ago | 1

Answered
Symbolic parameters not supported in nonpolynomial equations
vpasolve() has two different execution modes. If the system of equations is polynomial in all of the variables, then vpasolve()...

24 hours ago | 0

Answered
reading file in matlab
The code is intended to read binary files containing quadrature data. The code reads the entire file as a series of uint8 value...

1 day ago | 0

Answered
adding functions to path
The first line is a comment. The second file picks out the full name of the file that contains the executing code (mfilename('f...

1 day ago | 0

Answered
How to assign the number of filled columns of a text file as the value of a variable
detectImportOptions() might be your easiest method. Otherwise, fid = fopen('E:\A\nt.txt'); while true thisline = fgetl(fi...

1 day ago | 0

Answered
Save figure with a specific name
[filedir, basename, ext] = fileparts(filename); newname = fullfile(filedir, [basename '.png']); saveas(h, newname, 'png');

1 day ago | 1

| accepted

Answered
I got an error as symbolic function expected 3 inputs and received 1 in the line no 5 (g1{r}(u)=g1{r}(u)+(u{i}-u1(i))./5*chebyshevT(i-1,2*x(r)-1)). How can I fix that?
m = 3; x = rand(1,m-1); %replace with your actual data, which must be at least m-1 long v = rand(1,m+1); %replace with you...

1 day ago | 0

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Answered
How to Import/parse sparse data from a text file into MATLAB?
S=fileread('test.txt') ; data = str2double(regexp(S, '-?\d+(\.\d*)?, 'match' ) ; This code allows for negative data eve...

1 day ago | 0

Answered
I want to plot power of helicopters on y axis and name of helicopters on x axix.please help
categorical() the cell array of character vectors that are the helicopter names, and then plot() providing the categorical varia...

1 day ago | 0

| accepted

Answered
error with indices and vectors
MATLAB has no implied multiplication. A(1+i/12) is syntactically always either a request to execute a function indicated by A w...

1 day ago | 0

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Answered
How to resolve an error for forward substitution code?
m=[0.6000; 0.3704; 0.1311; 0.2629]; %sub diagonal of lower triangular matrix of A That is a column vector, one column. c(i)=b(...

1 day ago | 0

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Answered
What is "l"?
No, l did not have any special meaning. Is it possible that this is a nested function? Was there an end statement after what yo...

1 day ago | 0

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Answered
How to use an array as an input in a while loop
Your question requires that you plot with t2 as the independent variable and R4 as the dependent variable. You are currently lo...

1 day ago | 0

Answered
How to only change part of the background color?
set(gca, 'color', [1,1,1]) %instead of gcf

1 day ago | 0

| accepted

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