# J. Alex Lee

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**Content Feed**

Remove zoom from axes

This should be a good entrypoint: https://www.mathworks.com/help/matlab/ref/disabledefaultinteractivity.html https://www.mathw...

3 days 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...

4 days ago | 1

| accepted

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 ...

12 days 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...

17 days 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-...

27 days 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...

1 month 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...

1 month ago | 0

| accepted

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...

1 month 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...

2 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 ...

2 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...

2 months ago | 0

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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...

2 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...

2 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...

2 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 ...

2 months ago | 0

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...

2 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...

2 months ago | 0

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Iterating array of chars and saving to table or cell

Try this, if your function actually returns strings as your output suggests (rather than a char array) result = strings(length(...

2 months ago | 1

| accepted

Interpolate X-Y coordinates with variable velocity to specified sampling frequency

I don't think you need loops...so assume your data is called XYV, and according to how you describe, I guess the last velocity p...

2 months ago | 0

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How to interpolate between two adjacent points of time series data, if the difference between any two consecutive points is greater than 25 by using for loop?

If you just want the points to be "appear" roughly evenly distributed, you could consider spacing in the arc length (although yo...

2 months ago | 2

How to interpolate between two adjacent points of time series data, if the difference between any two consecutive points is greater than 25 by using for loop?

Here's [another approximate] way to do it that will only call spline once (could as well do it with gridded interpolant) The me...

2 months ago | 2

Randomly selecting images from a directory

Use "dir" and "randperm"

2 months ago | 0

| accepted

Why won't cells populate via if-else statements?

The if statements are probably your problem...you are comparing a column vector with scalars, which off the top of my head I don...

2 months ago | 0

Grouping age data into 5 year bins

Interesting, this could be useful for me too! You can use "discretize" to bin the data. Below is a quick and dirty class to impl...

3 months ago | 0

How to vectorize the following code for matrix insertion?

There is a minor point in David's answer, which is that not all index collisions are taken care of in how the g matrix is constr...

3 months ago | 1

| accepted

How to rotate 3D matrix?

it looks like your segment A is parallel to the axis OA (trivial in y-direction), in which case it should be easy to first trans...

3 months ago | 0

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1-D Temperature Gradient

your time and space point vectors are t = 0:0.005:50; % but this gives you 10,001 points, not 10,000...so you decide what you h...

3 months ago | 0

how to find the order of convergence

It sounds like you already implemented Newton's method, so just save all your residuals and plot [the log of norm] versus the pr...

3 months ago | 0

Saving each vector of an ode45 vector solution in a matrix.

Use a cell array instead z = cell(1,20) for i=1:20 G=i/20 %Saving that iterates value of G [phi,y]=ode45(@(phi,y) od...

3 months ago | 0

How can I generate values randomly from another existing vecor?

how about v1 = [122,34,20,5,21] v1a = [0,v1] N = numel(v1a) ridx = randi(N,size(v1)) v2 = v1a(ridx)

3 months ago | 1

| accepted