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J. Alex Lee


Last seen: 11 days ago |  Active since 2016

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Answered
Implementing Crank Nicholson in spherical setting
I believe this should be the right formulation for CN (taking a few liberties interpreting your problem). If you want speed, pr...

2 months ago | 0

Answered
Implementing Crank Nicholson in spherical setting
For one thing, your boundary conditions (as developed on your pdf) don't look right. At r=0, you can just directly use Eq 8 LHS...

2 months ago | 0

Question


Built in look-up style interpolation of timetables for non-numeric data?
Is there no built-in function similar to interp1 for numeric data, that can operate on timetables with arbitrary data types? So...

3 months ago | 1 answer | 0

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answer

Answered
For loop to carry value down depending on another matrix value
In your example, there is a "delay" by 1 row when your switch from 0 to -1 occurs, so the following answer is not exactly produc...

3 months ago | 0

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Answered
There used to be a function RefineMesh in Matlab used in solving ODE's, but it is now used for PDE's and isn't the same function. Is there a new function for the old purpose?
The workflow above only re-evaluates the "static" solution of ode45 at more data points by an interpolation scheme consistent wi...

6 months ago | 0

Answered
Is there a way to measure interletter spacing for Fixed Width font in MATLAB?
I have no idea what you mean by "visual angle per font size", but I know of one way: lbl = uicontrol("Style","text","String","...

7 months ago | 0

Answered
Functional programming construct to expand cell array into arguments for other functions without using an intermediate variable in the (user) code?
I am still not sure why you can't just have your generalized comparator function saved as a function somewhere on your path so y...

10 months ago | 1

Answered
How to integrate uidatepicker command with GUI interface?
Details are thin here...but it sounds like you need to first specify the parent graphics object that you want your uidatepicker ...

10 months ago | 0

Answered
How to solve exponential equation to find unknown constants
data = readtable("Book1.xlsx"); Alternatively, based on my reparameterization above you can as a first pass say everything afte...

10 months ago | 0

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Answered
How to solve exponential equation to find unknown constants
Do you have an intuition of what the graph of looks like? Hint: it looks like your plot, scaled and shifted roughly only in the...

10 months ago | 0

Answered
Print vectorized graphic of patches without edges
I now believe it is because you are technically plotting 3D patches (telling Matlab there's a z-coordinate, even if they are all...

10 months ago | 1

Answered
Calculations of Angle between two points
If you have the list of 3D coordinates rng(1) % control random generator NPoints = 5 vertices = rand(NPoints,3) You can defi...

10 months ago | 0

Answered
How to symbolically integrate f(T) = exp (E/(8.314*T) through integration by parts or with trapezoidal method?
The application still is unclear to me... If you just want numerical integration, look at the function "integral", as implement...

10 months ago | 0

Answered
Remove zoom from axes
This should be a good entrypoint: https://www.mathworks.com/help/matlab/ref/disabledefaultinteractivity.html https://www.mathw...

10 months ago | 0

Answered
Can I pass arguments to a @callbackFcn?
configureCallback(s,"terminator",@(src,evnt)readSerialData(src,evnt,operation mode)) So the first parentheses specify the inter...

10 months ago | 1

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Answered
I am trying to find the exact distance of a curvy line.
Assuming that the boundary points are ordered well (adjacently), then you can calculate the cummulative square distance between ...

10 months ago | 0

Answered
Take only some values from one array
you can't compare arrays of different lengths. a straightforward but cumbersome way is to cycle through each of your t1 and find...

10 months ago | 0

Answered
MATLAB GUIDE to App migration question
Apparently it should work: https://www.mathworks.com/help/matlab/creating_guis/compatibility-between-different-releases-of-app-...

11 months ago | 0

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Answered
How to Save new data to existing structure data in a for loop without having to save the complete Matlab file from Zero?
I would consider using a database, a lightweight solution could be sqlite. I use the third party mksqlite for this purpose and i...

11 months ago | 0

Answered
using varfun on a timetable with subscripts?
first of all, your operation looks like a "diff", no subscripts (for rows, i.e., timestamps) necessary second, you will be defi...

11 months ago | 0

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Answered
How can I quickly obtain the inverse of a square sparse matrix?
potentially, if you have more information about the properties of A, you can specify them in a call to linsolve https://www.mat...

11 months ago | 0

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Answered
3D/2D matrix multiplication without using a loop
I found this: pagemtimes() s = rand(5,5); x = rand(5,8,100000); tic y = pagemtimes(s,x); toc tic z = nan(size(x)); for...

11 months ago | 0

Answered
How to operate properly with multidimensional matrices and cells.
You might be looking for squeeze()? l=0; % preallocate C = cell(3,3,3); M = nan(3,3,3); % construct 3D cell and matrix ...

12 months ago | 1

Answered
How to solve a system of second order nonlinear differential equations with boundary conditions
This is a boundary value problem, so probably the most straightforward way is to use bvp4c or bvp5c if you want to solve numeric...

12 months ago | 1

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Answered
Backward and Central Difference
I guess the answer depends what you want to do with those finite difference approximations. If you want to use it in an algorith...

12 months ago | 0

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Answered
Save class object as struct
Look at this too: https://www.mathworks.com/help/matlab/matlab_oop/flexible-saveobj-and-loadobj-pattern.html I think it means w...

12 months ago | 1

| accepted

Answered
Can't get string to datetime conversion to work
str = '2019-05-17T19:36:00'; fmt = 'yyyy-MM-dd HH:mm:ss'; b = strrep(str,'T',' '); disp(b); timestamp = datetime(b,'Inpu...

12 months ago | 0

Answered
Auto Refresh in app designer.
in general for "auto refresh" you can use the timer object to schedule recurrent execution - disclaimer i have only played with ...

12 months ago | 0

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Answered
Using Hessian for least squares problem
Now that the actual question is clarified as a coding question and not a math question, it seems these should help: https://www...

12 months ago | 0

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Answered
Select rows in a given table according to 3 criteria
This is small enough you could generate the full list of combinations % generate all combinations alltriplets = nchoosek(1:7,3...

12 months ago | 0

| accepted

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