# J. Alex Lee

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**Content Feed**

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

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...

2 months ago | 1 answer | 0

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answerFor 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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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

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

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...

9 months ago | 1

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 ...

9 months ago | 0

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...

9 months ago | 0

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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...

9 months ago | 0

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...

9 months ago | 1

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...

9 months ago | 0

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...

9 months ago | 0

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

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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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

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

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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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

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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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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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

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 ...

11 months ago | 1

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...

11 months ago | 1

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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...

11 months ago | 0

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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...

11 months ago | 1

| accepted

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...

11 months ago | 0

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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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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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