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Walter Roberson


Last seen: Today Active 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. I am currently caught up to T0099000; if you are waiting on a reply from me for an older issue, please send me a reminder.

Programming Languages:
C++, C, MATLAB, Shell, Perl, Fortran
Spoken Languages:
English

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Answered
Converting values to units
values = randi([0 800], 1, 10) b = [-800 300 800]; mask = values < b(2); scaled(mask) = (values(mask)-b(1))./(b(2)-b(1)); sc...

4 hours ago | 0

Answered
how to calculate theta
Xo = 1234; V = 20000; syms theta t = .1:.1:1; eqn = 3010 == Xo + (V .* cosd(theta)) .* t thetas = double(arrayfun(@(E) vp...

8 hours ago | 0

Answered
Convert units to g
%need some data for demonstration t = seconds(0:0.5:10); y = randn(1, length(t)); %now do the work y_g = y ./ 9.80665; pl...

8 hours ago | 1

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Answered
add multiple lines to a single plot without using "hold on/off"
%% Create Plots % Would like pressure dist overlaid on airfoil shape tiledlayout(2,1); ax1 = nexttile; plot(ax1,x,y); hold(...

9 hours ago | 0

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Answered
Huge number of iterations
fcn = @() fopen( sprintf( 'chem_%d.txt', labindex ), 'wt' ); w = WorkerObjWrapper( fcn, {}, @fclose ); % a and b are cell arra...

10 hours ago | 0

Answered
How to loop over a function call?
y = [y1, y2, y3, y4] fun = @(x) reshape(sum(arrayfun(@(Y) Least_square(x(:), Y), reshape(y, 1, [])),2), size(x))

11 hours ago | 0

Answered
Can not shift image relative to plot with Imtranslate
and shown with imshow(image) I do not recommend imshow() for this purpose: it does too many things to the axes that are not des...

15 hours ago | 1

Answered
Initializing all rows with one set of values in one half and another set in the other half
cA(:,:) = repmat([cA0*ones(1,(N-1)/2+1),Kw/cB0*ones(1,(N+1)/2-1)], size(cA,1), 1); Or consider nrow = size(cA,1); cA(:,:) = [...

15 hours ago | 0

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Answered
Saving data array in Matlab data file (.mat) in App Designer
save('YourFileName.mat', 'NameOfVariable', 'AnotherVariable') Note that if the values you want to save are currently stored wit...

15 hours ago | 0

Answered
How to get same xlsread "raw" output whithout using xlsread?
mask = cellfun(@isdatetime, YourCell); YourCell(mask) = cellfun(@(DT) datetime(DT, 'format', 'dd/MM/yyyy'), 'uniform', 0); Now...

15 hours ago | 0

Answered
how to join the values of different cells in different columns in one cell ?
T.Date = datetime(T.Year, T.Month, T.Day, T.Hour, T.Min, 0, 'Format', 'uuuuMMddhhmm'); Note: I did not use the format you asked...

15 hours ago | 1

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Answered
Issue with numerical integration of two variable function
A = @(x, y) cos(x)+sin(y) B = @(x, y) A(x,y)-integral(@(X)A(X,y), 0 , 2*pi, 'ArrayValued', true) fsurf(B, [-pi pi -pi pi])

15 hours ago | 0

Answered
How to Solve matrix equations in Matlab
Optimal solutions, in the sense of smallest least-squared. Are there other solutions? Yes: you can ask to solve eqn2 with retur...

16 hours ago | 1

Answered
Finding 8 points on an ellipse
Refering to https://math.stackexchange.com/questions/493104/evaluating-int-ab-frac12-r2-mathrm-d-theta-to-find-the-area-of-an-el...

16 hours ago | 1

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Answered
Trying DIC 2D by ncorr
I notice that you are using a fairly old version of MATLAB. Still, uibuttongroup() should have been defined in your MATLAB. T...

18 hours ago | 0

Answered
Error in plotting an equation given y data sets (y vs x)
Your code wants to calculate the formula for each y value, for all possible x values. But to do that, you have to make the symbo...

18 hours ago | 0

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Answered
filtfilt fails with B=1, A=1 on matrix
It appears to be a bug. In context: filtfilt() calls filter() to do some of the work. When a and b are scalars, filter is goi...

19 hours ago | 0

Answered
Clear symbolic from an equation and make it mathematical function
syms x f=(17*exp((281*x)/50000))/1000 + (4777*x*exp((281*x)/50000))/50000000 ff = matlabFunction(f); x=4.5:1:40.5; plot(x,...

22 hours ago | 0

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Answered
how to find a float number
[is_there, idx] = ismembertol(-0.3340, y7) %options allow you to control tolerances y7(idx) Also, [~, idx] = min(abs(y7(:) -...

22 hours ago | 1

Answered
Solve a system of linear ODEs, and plot them
You built R as a column vector but your vector of constants 10^-7 and so on is a row vector. You will accidentally creating conf...

1 day ago | 1

Answered
Could someone please tell me why this code is printing(Dam level too low) for almost every output.
Newvol(k+1)=Newvol(k)+(Qin(k)-Qout); Newvol is a vector. if Newvol>=p100; You are testing the entire vector in that statemen...

1 day ago | 0

Answered
How to Plot a function that contains summation?
alpha = 8; m = (1:alpha).'; f = @(x) 2/pi + sum(2 .* ((-1).^m - 1)./(pi .* m.^2) .* cos( m.*x ), 1); fplot(f, [-pi pi])

1 day ago | 1

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Answered
graph won't plot in correct spot
If you do not want negative values shown, then clip them out of the plot by adjusting xlim and ylim. % plot mountain Mn_x = [0...

1 day ago | 0

Answered
how to assign imagesc to figure 1
fig1 = figure(1); ax1 = axes('Parent', fig1); imagesc(A1, 'Parent', ax1); If there is an existing axes you want to draw int...

1 day ago | 0

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Answered
Support for other Raspberry Pi operating systems.
Are there any plans to support other - non Raspberry Pi fundation based - operating systems / distros? No. There are too many L...

1 day ago | 0

Answered
I am finding it difficult to write extended langmuir isotherm using summation.
The meaning of that is not clear. The expression contains both and using exactly the same symbol . That tells us that the non...

1 day ago | 0

Answered
Please someone help me correct my code. I want to plot a 2D graph for distinct alpha in one single 2D plot. See the attached photo for the guidience
alpha=[0.7, 0.8,0.9,1]; P=1; t=0.5; s = (-5:0.2:5).'; A=(1-s.^2)+((P-4).*(t.^alpha))./(gamma(alpha+1)); plot(s,A); xlabel(...

1 day ago | 0

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Answered
Curve fitting with integral involved
format long g T = [120,210,400,540,650]; B = [-344,-157,-17.5,-0.85,10.5]; syms t y syms constant [1 2] expr = ((2.*pi.*(...

1 day ago | 0

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Answered
How I can modify this code to read files in a folder into tables?
nfiles = length(theFiles); results = cell(nfiles,2); fullnames = fullfile({theFiles.folder}, {theFiles.name}); results(:,1) =...

2 days ago | 1

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Answered
Displaying a set of images from a folder
projectdir = 'path/to/image/directory'; ext = '.png'; %adjust according to kind of images dinfo = dir( fullfile( projectdir, ...

2 days ago | 0

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