# Walter Roberson

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 T0099119; if you are waiting on a reply from me for an older issue, please send me a reminder.

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**Content Feed**

im trying to solve this system of 10 equations

M=10 deltax=2*sym(pi)/M syms f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 U1=f1*exp(1i*deltax)+f2*exp(1i*2*deltax)+f3*exp(1i*3*deltax)+f4*e...

24 minutes ago | 0

Solving a non-linear system of equations

You cannot. You have unknowns to a fractional power: the system cannot possibly be linear. You also have a^2*b which again is n...

1 hour ago | 1

Find location of 2 black dots in the image

See regionprops probably with 'Centroid'

2 hours ago | 0

Is Matlab 2012b still under support?

https://www.mathworks.com/support/requirements/previous-releases.html -- R2012b supported Windows 8, not Windows 10 at all. htt...

2 hours ago | 0

Differential equations by separable equations (Symbolically)

Math says that a diff eqn solvable by separable equations is one of the form f(x,y)=p(x)h(y) or p(x)+h(y)=0 For the first form,...

3 hours ago | 0

Error when importing data

you need to reinstall matlab. dbtype uiimport 1 should show function varargout = uiimport(varargin) but on your s...

17 hours ago | 1

| accepted

why tcpserver is not part MATLAB ? Why do I need to purchase instrument control toolbox ?

To be honest, I do not know why Mathworks made this decision. Earlier both tcp server and client were Instrument Control only, b...

18 hours ago | 0

what is the most efficient way to write multiple plots to the local drive?

Some performance tune-ups parfor i = 1:numel(data) persistent fig ax lines line_width = 1; if isempty(fig) ...

21 hours ago | 0

I am confused about why my code doesn't lead to a fitting result.

I had to fix every different things to get it to work. The improvement to summarize failed iterations instead of listing each o...

23 hours ago | 0

| accepted

Error message Error using mupadengine/feval_internal More equations than variables is only supported for polynomial systems. Error in sym/vpasolve (line 172) sol = eng.fe

Your T10 is a 4 dimensional array so your P becomes 4 dimensional. In order to vpasolve an expression involving that array, you ...

1 day ago | 0

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How to add trip_sum to table without error?

You have an existing trip_table variable that was built with a different number of variables. I suggest you build your table on...

1 day ago | 0

How to quickly view the variables in the mat file? My computer is poor, so it is slow to open matlab😭

https://comp.soft-sys.matlab.narkive.com/hkUdFzb0/quickly-list-variables-in-a-mat-file shows some C code that when compiled with...

2 days ago | 0

vpasolve unable to find solution of 6 simultaneous equations

You need to arrayfun or loop over elements of V_i as vpasolve and solve try to solve all of the passed equations simultaneously ...

2 days ago | 0

I need help to solve this problem, I don't understand why it's not working

configure the arduino and servos *once* in Classroom_security_OpeningFcn not in every callback. Also use try/catch in ca...

2 days ago | 0

help to find error in this?

https://www.mathworks.com/help/matlab/math/parameterizing-functions.html global is not recommended

2 days ago | 0

Dimension 1 is fixed on the left-hand side but varies on the right ([512 x 512] ~= [:? x :?]).

in the interface block you specified the signal size as 512 by 512. It is not marked as variable sized, and the 512 512 will *no...

2 days ago | 0

Conversion of (129x7 complex double) to an Image

you could use the tiff gateway and write the imaginary component as unassociated alpha. There is an example at https://www.ma...

2 days ago | 1

I can not use log function in matlab

Your MATLAB installation is corrupted. You need to reinstall it.

2 days ago | 1

Define a family of functions

If you *could* define a "family of functions" in MATLAB, what properties would you want such a thing to have? If there were clas...

2 days ago | 0

Error using feval Function to evaluate must be represented as a string scalar, character vector, or function_handle object.

syms t f(t)=[-cos(t), -sin(t), 2*cos(t)^3 - 7*cos(t)*sin(t)^2] Then output = feval(f,3.14) %must "use" the output or f(3....

3 days ago | 0

How to solve Multivariate equations

syms s phi theta; First you create symbolic variables. The MATLAB level variables s phi and theta will be assig...

3 days ago | 0

The embedded function "allSimplePaths" in the allpaths.m

allSimplePaths is a built-in method % matlab.internal.graph.MLDigraph method It is an undocumented internal function.

3 days ago | 0

| accepted

How to have legend coloured according to data

I suggest you consider using gscatter Otherwise, you have two possibilities: use one scatter() call for each different group, ...

3 days ago | 0

| accepted

Is it possible to select two points automatically from an image?

Information can only be automatically extracted if there is a programmable rule that describes how to distinguish the informatio...

3 days ago | 0

How do you ask the user to load a path from the .xlsx file, then store it in variables with some concerns when reading the .xlsx file using app designer?

I opened in the file in Excel. In the first sheet in the file, "AC No ESS", there are only 5 columns, and readtable() finds them...

3 days ago | 1

Why is my FFT diagram has a slope approaching to zero?

Fs=1000; T=1/Fs; t1 = readtable('t.xlsx'); L = width(t1); t = t1{1,:}; S = t1{2,:}; plot(t,S) f=Fs*(0:(L/2))/L; Y ...

3 days ago | 0

Is it possible to call parfeval from within a parfor loop

No, that is not possible. See https://www.mathworks.com/matlabcentral/answers/1904941-dual-parfor-from-different-scripts#answer...

4 days ago | 0

How can I make my 'x' matrix in scatterplot in 2 different colors??

scatter() can take information about color in the 4th parameter. The color information can be set per-point. xdata = repmat(Tem...

4 days ago | 1

How can I make my 'x' matrix in scatterplot in 2 different colors??

A different approach would be to use gscatter xdata = repmat(Temp, 5, 1); ydata = [Bin1; Bin2; Bin3; Bin4; Bin5]; g = 2 * one...

4 days ago | 1

Save each loop from getfield command

It is not clear to me why you are using that getfield instead of ffextract = fftrials{1,1}(1,n).df; You have for n=1:size(fft...

4 days ago | 0