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Walter Roberson


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47,244 total contributions 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.

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Answered
Uploading Exact data from Excel
readtable(). You are probably seeing excel date numbers, which are relative to Jan 1, 1900

3 hours ago | 0

Answered
Undefined function 'diff' for input arguments of type 'cfit'.
<https://www.mathworks.com/help/curvefit/sfit.differentiate.html> differentiate() not diff() You will need to pass in the loca...

4 hours ago | 0

Answered
Using loops for an initial condition change
Break it up into two callsz one with timespan ending at that time, and the second starting from that time. Copy the end boundary...

4 hours ago | 0

| accepted

Answered
Plot xx mark after a threshold
Draw the complete data once with 'b'. Then "hold on". Then draw the same data again with 'r*' and with 'MarkerIndices', find...

5 hours ago | 0

Answered
"receive" command of the "Vehicle Network Toolbox" does not track more than 546 points in Matlab
receive() is limited to returning messages that are already queued. We can therefore detect that in the system you tested, th...

6 hours ago | 0

Answered
Cell elements must be character arrays. (Solver equations created in a loop)
eqns_all = [eqns_all;{eqn}]; solve() cannot process a cell array of equations. You should leave out the {}

7 hours ago | 0

Answered
Plotting signal using MATLAB function
Arrgh! my browser ate my long reply explaining what you were doing wrong! So I am going to skip all of that and tell you to ...

7 hours ago | 0

Answered
How can you clear the content of a workspace in the MATLAB environnement
Three types of errors in MATLAB are: * conceptual * ecumenical * denotational

8 hours ago | 0

Answered
Running .m and simulink (.slx) file together
Use persistent. Check if the persistent variable is empty and if it is then configure it. Then either way, read from the daq. ...

11 hours ago | 0

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Answered
Given that A is a sparse matrix, norm(A(i,:)) takes a very long time. Why and can one do better ?
If you were going to do this repeatedly, then %one time cost At = A.'; %then norm(At(:,1)) is over 100 times faster than ...

12 hours ago | 0

Answered
How to correct unexpected behavior of `regexprep`?
?: is "group but do not capture" so the () within it do not capture. One approach: regexprep('my.file.ext', {'^([^.]+)$', '^(....

1 day ago | 0

| accepted

Answered
Empty sym: 0-by-1
t6 = th6_;d6 = L;a6 = 0; alpha6 = 0; so t6 uses th6_ A6_= inTransMat(a6,alpha6,d6,t6); and A6_ uses t6, so A6_ uses th6_ T_ ...

1 day ago | 0

| accepted

Answered
How to use dicomwrite after modification
You are constructing file names for all the dcm files in the directory. You iterate over each one, displaying a file name approp...

1 day ago | 0

Answered
fmincon does not converge to the best solution?
fmincon can return a value that is worse than the initial point in some cases, especially if you are using interior-point. It wa...

1 day ago | 0

| accepted

Answered
Purchase of toolbox without credit card?
Businesses and educational institutions can (normally) use Purchase Orders. Individuals, businesses, and educational institutio...

1 day ago | 0

Answered
Convert .mat file into .xls file
Your .mat file has two variables that are completely different. Although it is possible in theory to put both variables into the...

1 day ago | 0

Answered
How to use ezplot
https://www.mathworks.com/help/matlab/ref/fimplicit.html is recommended these days. ezplot(@(x,y)x.^2 - 9*y.^2 - 81)

1 day ago | 1

Answered
I tried to import an image in MATLAB that was on my desktop but it returned an error. Please help me out for this
Your current directory is probably not the desktop. The desktop is not on the default matlab path. ls *.jpg

1 day ago | 0

Answered
Rounded random numbers with fixed sum
https://www.mathworks.com/matlabcentral/answers/327656-conditional-random-number-generation#answer_257296 Multiply your desire...

1 day ago | 0

Answered
Reading a hex table with some undefined values
filename = 'hex.txt'; missingindication = {'0xXXXXX'}; data = readtable(filename, 'treatasmissing', missingindication, 'read...

1 day ago | 0

Answered
MATLAB App designer 2019 a
readtable() and set the table itself as the Data property of a uitable() . Use a CellSelectionCallback https://www.mathworks.co...

1 day ago | 0

Answered
How to convert tif stack to dcm series?
fname = 'Sample19.tif'; info = imfinfo(fname); imageStack = []; numberOfImages = length(info); for k = 1:numberOfImages ...

1 day ago | 0

Answered
ttest error - undefined variable - error nanmean nanvar etc.
Error in nanvar (line 29) coder.internal.assert(eml_is_const(dim), ... In R2016b, the release you are using, nanvar has 30...

1 day ago | 0

Answered
Undefined function 'sqrt' for input arguments of type 'char'.
cwt(bigcircle_ant2_data,'amor',1); %produce plot-morlet You are using the calling syntax for newer versions of cwt...

1 day ago | 0

Answered
C = union( A,B ) is too slow. Is there any faster way given that A and B are ordered.
The faster way would involve writing some mex code. There is an undocumented internal binary search routine, but calling it repe...

1 day ago | 0

Answered
What type of error is this?
You accidentally save()'d variables on top of a code file. The code is gone. But you might be able to get something useful fr...

1 day ago | 0

| accepted

Answered
Function implementation matlab language
https://www.mathworks.com/matlabcentral/answers/576745-shifting-handling-in-matlab-with-for-loop#answer_476968

1 day ago | 0

Answered
Can I run eigs on a GPU?
eigs really is not supported. https://www.mathworks.com/matlabcentral/answers/572377-accelerate-eigs-with-gpu#answer_472900

1 day ago | 1

Answered
C code generation symbols not found linker error
https://www.mathworks.com/help/images/ref/imadjust.html#bvm6s9t-1 imadjust generates code that depends upon a shared library t...

2 days ago | 0

Answered
calculating error while averaging multiple images
Do you want the average of the R, G, and B separately for each image? Are you asking for averages to be taken over time for ea...

2 days ago | 0

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