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Walter Roberson


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50.040 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
Array in a symsum
You are attempting to index x with a symbolic variable. That is not possible with MATLAB, and that is something that is not expe...

etwa 8 Stunden ago | 0

Answered
How to fix error message "Invalid pfile. The file header is corrupt."
You cannot fix it yourself. You need to get the site to recreate the file. However, it is possible that the p file was create...

etwa 10 Stunden ago | 0

Answered
I am trying to test a part of my code but it shows me this message ! how can i solve it , Help plz !
for k=1:1:lenght(Material) You have not defined any variable named Material but you have defined a variable named material...

etwa 12 Stunden ago | 0

Answered
roots of non linear periodic function
format long g rng(655321) L = randn() P = rand() * 10 C = @(x) x.*L.*tan(x*L)-P root1 = fzero(C, pi/3) N = 10; nroots...

etwa 12 Stunden ago | 0

Answered
evaluation of anonymous function
In that code, V is never evaluated. In that code, MATLAB sees the @(x) (0.5+0.5.*sign(r.^2-x.^2))*V0 part and constructs an ...

etwa 12 Stunden ago | 2

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Answered
Help with Surrogate Modeling Multivariable Objective Function
Yes, you should be able to do that. Construct lb and ub vectors (mandatory!! and must be finite!) that are length() equal to the...

etwa 13 Stunden ago | 0

Answered
Reduce symbolic fraction by powers of ten
load sample; syms s G = YQ_sym(1,2); vpa(G,5) vpa(simplify(G),5) [N,D] = numden(G); Dc = coeffs(D,s); FN = factor(N);...

etwa 13 Stunden ago | 1

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Answered
how to get average of multiple rows and subtract from one group of average to another
M = your matrix with 10039 rows and 64 columns N = 30; whole_blocks = floor(size(M,1)/N); leftover = size(M,1) - whole_blocks...

etwa 14 Stunden ago | 0

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Answered
Normalization of symbolic expression
syms L R K b J s v a1 = det ([(L*s+R) (v); (-K) (0)]); a = det ([(L*s+R) (K); (-K) (J*s+b)]); g=collect((a1/a)*(1/v),s); G=s...

etwa 14 Stunden ago | 0

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Answered
How can I add multiple 1 x 1 strings to all rows in a table?
https://www.mathworks.com/help/matlab/ref/table.addvars.html You can use 'Before' and 'after' to add the variables into a part...

etwa 14 Stunden ago | 0

Answered
Merge two figures into one
TextFontSize=20; LegendFontSize = 18; set(0,'DefaultAxesFontName','Times',... 'DefaultLineLineWidth',1,... 'DefaultL...

etwa 15 Stunden ago | 0

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Answered
Putting two FAS figures into one.
Remove the call figure; Add the call hold on after the plotting

etwa 15 Stunden ago | 0

Answered
Automatically load a csv file from a folder
EEGDIR = '/Users/roberson/Plan9/Dhort/ECGData'; tries = 42; found = true; for trynum = 1 : tries random_MaleShortName = ...

etwa 15 Stunden ago | 0

Answered
Displaying a value using fprintf with certain number of decimals.
format long g a = rand*10 fprintf('The answer for a is %.2f m/s\n', a)

etwa 15 Stunden ago | 1

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Answered
solution of ordinary differential equations when there is a f(t)
I don't know what's C8 and should I just take the (-exp(2*C8 + 2*t)/(exp(2*C8 + 2*t) - 1))^(1/2) as the correct solution? Yes? ...

etwa 15 Stunden ago | 0

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Answered
Acquire data from smartwatch sensors via USB
That is going to depend in part on the smartwatch. I just tried with an Apple Series 3 smartwatch. The charging cable is a USB-...

etwa 16 Stunden ago | 1

Answered
Problem with code originally written for MATLAB R2006a -- problems with break statement
Long ago, no error message was generated for a break outside of any loop. I never used that behavior myself... I think I encount...

etwa 16 Stunden ago | 0

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Answered
Finding inverse Laplace when the inverse Laplace function is a piecewise function
rewrite(x, 'piecewise')

etwa 17 Stunden ago | 0

Answered
Rotating a meshgrid in 3D
The 3d process is much the same, except that you build xyz columns and multiply by a 3x3 array. It can be easier to use makeg...

etwa 17 Stunden ago | 0

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Answered
MEXFILE error, libmex.dylib not loaded
You might need to do DYENV = 'DYLD_LIBRARY_PATH'; olddy = getenv(DYENV); path_to_add = fullfile(matlabroot, 'bin', 'maci64');...

etwa 18 Stunden ago | 0

Answered
hour of datenum type
datetime("now") Okay, creates a datetime object and lets it be displayed month(datetime("now")) Okay, creates a datetime obje...

etwa 19 Stunden ago | 0

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Answered
How to replace x or y axis tick values with texts
x=[1,3,4,6]; y=[20,40,50,80]; plot(x,y); yticks([20,40,60,80]) yticklabels({'white', '\color{red}red', '\color{green}green', '...

etwa 20 Stunden ago | 0

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Answered
Solve the following simultaneous set of nonlinear trigonometric equations:
c1 = 0, c2 = 0, c4 = 0, c5 = -1000, c6 = 0, d3 = -500, s1 = 1/1000, s2 = -1, s4 = -1/s6, s5 = 0, s6 = s6 c1 = 0, c2 = 0, c4 =...

etwa 20 Stunden ago | 1

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Answered
Can you run third party applications multiple times with MATLAB for analysis?
Sometimes it is possible. It depends on the application, on whether it accepts command line arguments; and if you are using MS W...

etwa 21 Stunden ago | 0

Answered
Cannot convert double value 0.01 to a handle.Cannot convert double value 5 to a handle.
format long g fig = figure(1); fig class(fig) %notice it is a handle fig.Number %that has an associated integer H1 ...

etwa 22 Stunden ago | 0

Answered
Unable to perform assignment because the left and right sides have a different number of elements
if 0 <= t(i) && t(i) <= 8 V(i) = 10*t(i).^2-5*t(i); Also else t(i) > 26; That calculates whether t(i) is g...

ein Tag ago | 1

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Answered
pre allocating variables in matlab
That's not what I get. imgThresh = im2bw(imread('image.png')); rows = size(imgThresh,1); columns = size(imgThresh,2); x=...

ein Tag ago | 0

Answered
Printing and Plotting after each loop
A=[1 3 4;3 5 6] U=[] for i=1:10 A = A * 2; U=A; dlmwrite('U.txt', U, '-append') end !cat U.txt

ein Tag ago | 0

Answered
How to check a change in one quantity given a known in a separate but related quantity
format long g A = randi([0.5e10 6e15],1, 100); B = rand(1,100)*6-3; mask = A(2:end)./A(1:end-1) >= 10; Bdiff = diff(B); c...

ein Tag ago | 0

Answered
YALMIP is not working with parfor loop
YALMIP permits you to define variables using calls such as P = sdvpar(1) and it expects that variable to be distinguished from...

2 Tage ago | 0

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