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Walter Roberson


Last seen: Today
50,533 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
Error: Error using dlfeval Value to differentiate must be a traced dlarray scalar.
Notice the example code has f = 100*(x(2) - x(1).^2).^2 + (1 - x(1)).^2; grad = dlgradient(f,x); so it is receiving an x (tha...

5 minutes ago | 0

Answered
how to plot time-based x-axis?
numtime = 17; %or whatever timevals = linspace(0, maximum_time, numtime); arr_throughput_A = zeros(max_num_stream,numtim...

5 hours ago | 0

Answered
how to read and plot a .trc file?
The trc file you sent me is in Lecroy Binary Format. Fortunately someone has created code to read those. https://www.mathworks....

6 hours ago | 0

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Answered
Calling script from a function is recommended?
% bar.m fid = fopen('baz.m', 'w'); fprintf(fid,'beta = 1:1e6;\n'); fclose(fid) whos baz(); whos clearvars foo() whos ...

6 hours ago | 0

Answered
[Feature request] "Run from Start to Here" button in Live Scripts
In the Live Editor, mouse over to the white border between the line numbers and the gray space for the code. A "Run to Here" but...

6 hours ago | 0

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Answered
Filter or delete data from (time)table depending of missing values
[Copying answer down from comments] Snan = @(v)sum(v) + 0/(numel(v)==6); datasum = rmmissing(retime(data, 'hourly', Snan)); (...

7 hours ago | 0

Answered
scatter3, stop the color changing after a second scatter3 command
When you use scatter3() and pass in a vector of color information, the information you pass in is not color indices into the cur...

11 hours ago | 1

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Answered
using fzero to solve nonlinear equation
The function handle you pass to fzero() or to fsolve() must accept only one parameter. Your s0, vmax, and k are all known cons...

13 hours ago | 0

Answered
filtering data from table
Close. TQTable = timetable(Time, Temperatuur, GlobalStraling);

13 hours ago | 0

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Answered
minor grid in consecutive plots
grid minor toggles the visibility of the minor grid lines. Minor grid lines lie between the tick marks. Not all types of charts ...

14 hours ago | 0

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Answered
loading a sequence of datasets using parfor
You need to synchronize with the GPU, and spend time transfering data to it, and wait for it to be ready, and read the data back...

15 hours ago | 0

Answered
Unable to perform assignment because the left and right sides have a different number of elements.
S = zeros(1,T/dt); S(1) = N; S is a vector. dS = ((-beta*(B/(B+k))*S(tt) + ub*(S(tt)+I(tt)+R(tt)) - ud*S) * dt)'; ...

15 hours ago | 0

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Answered
How to find and store each spot center position in the loop.
Use bw = bwareafilt(imbinarize(croppedImage), [10 inf]); Some of your images end up with very small extra regions, jus...

15 hours ago | 0

Answered
Plot time series data colored by color coded by ID
t = readtable('YourFile.csv'); [G, ID] = findgroups(t{:,1}); hold on h = splitapply(@plot, t{:,2}, t{:,3}, G); xlim auto; yl...

16 hours ago | 0

Answered
Switching between functions that have the same name
You do not need to restoredefaultpath but you do need to remove the previous folder You do, however, need to clear the class. ...

16 hours ago | 0

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Answered
How to stretch cos fit
axes([0 0.75 0.75 1.03]); %must do this before plot h(1) = scatter(xData, yData, 'b+', 'DisplayName', 'data'); hold on h(2)...

17 hours ago | 0

Answered
subplot for 'controlchart' function
Use the 'parent' option ax(1) = subplot(2,1,1); plot(ax(1), rand(1,20)); ax(2) = subplot(2,1,2); load parts st = contro...

17 hours ago | 1

Answered
Why symvar() sort 10 smaller than 9
symvar() sorts inconsistently if I recall correctly. It gets complicated when you start mixing numbers and underscores. For the...

17 hours ago | 0

Answered
How to use else if with ODE45 solver?
The mathematics used in the RK methods such as ode45(), require that for any one call the function be continuous and its first t...

17 hours ago | 0

Answered
How to avoid rounding error
A = [sym(10)^(-20) 1 ; 1 2] [L,U] = lu(A) L*U - A You can see from this that in order to get back A exactly, then you need a ...

17 hours ago | 0

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Answered
How to achieve identical timing of two side by side annotations
For anything like this you should probably be using the third party Psychtoolbox http://psychtoolbox.org/

18 hours ago | 0

Answered
How to use movefile correct?
files = dir('/Users/haron/Desktop/Work/Haron/aprikose_edfs/*.edf.html'); for ii=1:length(files) oldname = fullfile(files(...

1 day ago | 0

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Answered
performing multiple elementwise operations at the same time
You would need the Parallel Computing Toolbox... and a flexible definition of "at the same time". It is unlikely to be worth th...

1 day ago | 0

Answered
what's the problem with my code ? Warning: Rank deficient, rank = 1, tol = 2.574115e-12.
for i = 1:n_pts+1 a = [X1 Y1]; Your X1 and Y1 do not change with the iterations, so your a will be the same for all iterations...

1 day ago | 0

Answered
How to use #inlcude <>? # is declared as an invalid character!
MATLAB will not tell you that if your file extension is .c

1 day ago | 2

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Answered
correlation between binary strings
R = sum((x - E).*(y - E)) ./ (sqrt(sum((x-E).^2)) .* sqrt(sum((y-E).^2)));

1 day ago | 0

Answered
Warning: Integer operands are required for colon operator when used as index.
If length(V2) is even, then length(V2)-1 is odd, and length(V2)-1)/2 would not be an integer when you do the 0:1: operation. Lik...

1 day ago | 0

Answered
Need help to mask the image.
img = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/578172/untitled.jpg'); grimg = rgb2gray(img); bla...

1 day ago | 0

Answered
Use the input arguments to load user-defined .mat files(2xn matrix) in the function.
A= load (varargin{1}); %to load first inputargument file name This assumes that when you called [Ans1,Ans2,Ans3,Ans4]= Data_fu...

1 day ago | 0

Answered
Calling Matlab from command line gives Caught unexpected exception of unknown type, why?
clear all; clear all asks MATLAB to destroy as much state as possible, leaving little more than what is stored in the current g...

1 day ago | 0

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