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Walter Roberson


42,310 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
Assigning indexes in an array and finding max values in a selected range
Assuming that X is a timeseries object (and not a Simulink time series): rstart = 4000; rend = 5000; [maxabs, maxidx] = max(X....

2 hours ago | 0

Answered
Plot a contour that changes with respect to time
[~,ch] = contour(long, lat, YourMatrix(:,:,1)); drawnow(); dt = diff(timestep); for timestep = 2: size(YourMatrix,3) ...

2 hours ago | 0

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Answered
Solving equation returns a 0x1 sym
N=1000; T1=300; V1=.002; V2=1*10^-5; h=6.626*10^-34; kb=1.38*10^-23; g=3; Sigma=2; Thetav=2256; m=3*10^-26; r=(1.21*10...

3 hours ago | 0

Answered
How to create a 4D plot.
x = 0:.01:1; y = x; z = x; [X,Y,Z] = meshgrid(x,y,z); mask = X.^2 + Y.^2 + Z.^2 <= 1; F = sqrt(1-(X.^2+Y.^2+Z.^2)); %cauti...

4 hours ago | 0

Answered
The ode45 function only outputting constant value
exp(-45.49/R*T) is exp(-1500-ish) which underflows to 0. Your input temperature would have to be below about 136 K in order for...

5 hours ago | 1

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Answered
Help with this problem please
if ~any(A(i,j) == [0; 1]) Note that as soon as you find the first place, then you know the answer for the entire matrix, so you...

5 hours ago | 0

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Answered
problem with graphics to use surf()
cor2 is periodic. It ends up starting and ending at 0. You use it to form the Y coordinates, and in so doing accidentally ask th...

5 hours ago | 0

Answered
How to make matlab output a matrix in engineering notation?
Give the command format short e %engineering notation always or format short g %most convenient notation To get more ...

5 hours ago | 0

Answered
Add different numbers to numbers in vector and have multiple output vectors
bsxfun(@plus, [1,-1,i,-i].', YourRowVector) Or if you have R2016b or later, [1,-1,i,-i].' + YourRowVector These will give a 4...

5 hours ago | 0

Answered
how to transform this code to guide
The code would be the same in GUIDE. See however http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functio...

5 hours ago | 0

Answered
Why do I get "Array indices must be positive integers or logical values"
Please read https://www.mathworks.com/matlabcentral/answers/453477-error-array-indices-must-have-positive-or-logical-values#answ...

5 hours ago | 0

Answered
Optimization that does not repeat same evaluation
You could continue to use ga(), but memoize() the function so that if it were to be called with the same parameters again then i...

8 hours ago | 0

Answered
How to change specific number in a specific line in text file?
in_filename = 'YourInputFileNameGoesHere.txt'; out_filename = 'YourOutputFileNameGoesHere.txt'; S = regexp(fileread(in_filen...

8 hours ago | 0

Answered
How to plot contour of 3rd independent variable on top of 2D plot
N = 50; numlevel = 25; [X, Y] = ndgrid(linspace(0,0.5,N), linspace(0,1,N));; Z = griddata(x, y, z, X, Y); contourf(X, Y, Z, ...

9 hours ago | 0

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Answered
Binary File Writer in Simulink
It is not possible in any current release to bring the file name in on a port or to specify the name of a variable or data regis...

11 hours ago | 0

Answered
matlab invalid expression issue
solar_cell = @(V_mp) exp((q.*V_mp)./(kb.*T(k)))) <-- too many ) at this point

23 hours ago | 0

Answered
Why do I get NaN values? How to Fix?
rank(A) is 7 rather than 8. At some point in the processing, it will encounter a row whose content can be represented as a linea...

1 day ago | 0

Answered
How do I fix index, I keep getting an error
When you created A, you used commas. Change those commas to semi-colons. Your current A is a vector instead of a 2D array.

1 day ago | 0

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Answered
Plotting A Matrix Using Surfc
Your T is created as 3 dimensional. You are trying to surfc() a 3D volume. surfc() and surf() are only for 2D arrays (on a plane...

1 day ago | 0

Answered
How can I remove holidays from a timetable
https://www.mathworks.com/matlabcentral/answers/388366-removing-weekends-and-holidays-from-a-timetable

1 day ago | 0

Answered
I do not know if its a symsum function i have to use
It looks to me as if it is likely that q and t represent vectors that are being indexed. You cannot use symsum() to index a vect...

1 day ago | 0

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Answered
Finding row numbers of a matrix where certain column entries match a criterion
find(C0(:,2) == 4 & C0(:,3) == 3)

1 day ago | 0

Answered
scxsc Mapping Toolbox, Can the Precision Change?
At the command line, give the command format long g and then display the output variables again. You will see that they have m...

1 day ago | 0

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Answered
Replace all numbers in a cell array that are less than 10 to 10.
cellfun(@(C) cellfun(@(M) max(M,10), C, 'uniform', 0), YourOuterCellArray, 'uniform', 0)

1 day ago | 0

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Answered
How to add a picture in the 3D-plane
warp() is the most straight-forward way of displaying an image on an arbitrary surface. surf() and patch() can do the work if yo...

1 day ago | 0

Answered
How to convert time format
datetime(TheString, 'InputFormat', 'uuuu-DDD''T''HH:mm:ss.SSS') Note that this date does not include any timezone information. ...

1 day ago | 1

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Answered
strange symbol instead of legend color
The strange lines in the legend are the legend entries for the errorbar() If you only want the bar() call to be legend'd then r...

1 day ago | 2

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Answered
How to extract the following number from a text file?
filename = 'output_matlab.txt'; S = fileread(filename); phd_str = regexp(S, '(?<=^Pile-head deflection\s+=\s+)\S+', 'match', '...

1 day ago | 1

Answered
why is inv of matlab not working like numeric::inverse of mupad?
numeric::inverse processes the numbers symbolically. The default conversion is floating point to nearby algebraic numbers or pi....

1 day ago | 0

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Answered
UNDEFINED VARIABLE ERROR AFTER EXECUTING FOR LOOP IN MATLAB
You did not initialize columnMatrix, and numel(listOfImages) was 0.

2 days ago | 0

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