Ahmed A. Selman

Last seen: 10 days ago | Active since 2013

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Ph.D. in theoretical nuclear physics, author of four books and lecturer at the College of Science-University of Baghdad since 2008. Interested with image processing applications in astronomy mainly. I begun using Matab since the year 2000 (I think it was ver.5.), and still there is much to learn about. Professional Interests: Theoretical Physics

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MATLAB
Spoken Languages:
Arabic

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Answered
Help naming text file according to user input
Just add the extension you like to the variable (fileName), as prompt = 'Please enter the file name: '; fileName = input(...

11 years ago | 4

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Answered
how to find the second order partial derivative of an image?
See older and similar question here: <http://www.mathworks.com/matlabcentral/answers/67893>

11 years ago | 0

Answered
Reshape array for 256 by 256 matrix showing 16 by 256
Dear sudipta, I have downloaded your data file, and went like a=load('1372387722318.txt'); y=reshape (a,256,256); ...

11 years ago | 0

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Answered
Save 512x512 matrix to text file
This code works perfectly. To check it add the following at the very end of the above code: fid = fopen('Mymatrix.txt','r'...

11 years ago | 0

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solve 2 equation of 2 unknown
Use the code instead: clc clear syms theta3 r1 %sind(theta3) % NOT NEEDED r2=3; r3=3.927; r4=0.335; ...

11 years ago | 1

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Answered
extracting submatrices from cell
Try the same example with: X={1, 'a'; 'b', 3.14}; K1=X(2,:) [K21 K22]=X{2,:} Then use whos to...

11 years ago | 0

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Answered
How to identify boundaries of shapes in an image using the change in color
There are few files in the file-exchange <http://www.mathworks.com/matlabcentral/fileexchange/> so do some search there, you mig...

11 years ago | 0

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error message using polynom
A polynomial P(x) is said to be (badly conditioned) when a small variances of x leads to large errors of P, causing unstable err...

11 years ago | 0

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Creating a matrix with matrices on the sub and super diagonals
Use the command (diag) for creating a (main) diagonal matrix from a vector A, and the command (spdiags) to create sub- and super...

11 years ago | 0

Answered
Picking out a value from a Vector in a Loop iteration
Within your same code: ... plot(Y(:,1),Y(:,2),'o'); z=zeros(1,length(X)); % Add this for i = 1:length(X) f...

11 years ago | 0

Answered
More help with probability...
Just pay attention to how you use function call inside a program. Either you have two files as stated above, or use one main (ca...

11 years ago | 0

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Answered
How to plot with a logarithmic scale?
semilogx(x,y)

11 years ago | 2

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Answered
how to solve loops conditions ??
#1) Using for loops only: clear k=0; for i=1:6 for j=1:5 k=k+1; A(i,j)=k; end end ...

11 years ago | 0

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Symbolic expressions: abs(x^(1/3)) =?= abs(x)^(1/3)
Some times we get confused between mathematics and programming, it is an often thing. Yet, mathematics means logic, programs try...

11 years ago | 0

Answered
how to write a .dat file in matlab?
The obvious method is to construct a loop to read filenames, inside it, open and read, then accumulate the data content in some ...

11 years ago | 0

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Answered
Reading many files in one loop
Download a function file called folderFiles.m. <http://www.mathworks.com/matlabcentral/fileexchange/40877-folderfiles-m> ...

11 years ago | 0

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Answered
How to read a text file line by line?
Try selecting one dimension a time for each line, e.g., ... time=fscanf(fID,'%g',[1 1:2:inf]); acce=fscanf(fID,'%g',[...

11 years ago | 0

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Obtaning a matrix with the right indexes
Try this out to see if it solves the issue: clear clc N=20; %for example H=sym(zeros(N,4)); B=1:N; ...

11 years ago | 0

Answered
How to create a nested for loop to create a mesh plot
I'm not sure what are your conditions (in the if statements), but you used (y1) as a matrix index which cannot be made unless (y...

11 years ago | 0

Answered
Hi all, could you please help me to solve this equation either numerically of symbolically.
If all variables other than (y) are known, then let's write some notes here: 1) Try to first define the variables, namely: kw...

11 years ago | 0

Answered
Issue with writing multiple variable to excel sheet
It is not practical to write a single line in an excel file, for a large amount of data or inside a long-time running loop. If y...

11 years ago | 1

Answered
while loop question number 2
In such a case, using a while loop cannot do the job, but an if statement can. So, I think this is what are you looking for (con...

11 years ago | 0

Answered
How to plot a complicated function
It is the same code you wrote, only add loops over c and tau, and use the function (ezplot) to plot a function handle. And DO NO...

11 years ago | 0

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Answered
how to code probability in general??
First what is magic(2)? I thought the smallest magic matrix comes (3-by-3) since Magic (2) doesn't satisfy the condition (sum ea...

11 years ago | 0

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Answered
Lighting the Solar System - Omnidirectional light source (Sun)
I don't know really if Matlab is used for such tasks, but haven't you tried Simulink for easier handling of the problem? Such gr...

11 years ago | 0

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while loop in data file for trapz?
Apparently, the variable (Num) is not (1). That's why the (while loop) returns nothing. I've tried the lines you posted and it w...

11 years ago | 0

Answered
Switch columns in a matrix without a loop
for exchanging two columns 3 - 9 : A = randi(20,4,10); % A random 4 by 10 matrix of integers A(1,:)=[1 2 3 4 5 6 7 ...

11 years ago | 0

Answered
I WANT TO SOLVE THE EQUATION for x: x*exp(x)=(a1-x)*a2*a3 . Here a1 and a3 are matrices and a2 is a constant. I cant solve the equation using solve
True, indeed. Not only for (A,B) = (11,13) and (3,-6), but for a wide range of other set, including the given coefficients.....

11 years ago | 0

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Answered
I WANT TO SOLVE THE EQUATION for x: x*exp(x)=(a1-x)*a2*a3 . Here a1 and a3 are matrices and a2 is a constant. I cant solve the equation using solve
The equation you wrote is x*exp(x)=(a1-x)*a2*a3 y= x*exp(x)-(a1-x)*a2*a3 y= x*exp(x)-a1*a2*a3 +x*a2*a3 Let: a1*...

11 years ago | 0

Answered
how to find the sum terms in of binomial expansion
The general steps to find such a summation are: - Start a loop over r, - Calculate each term as a function of (r), - I...

11 years ago | 1

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Ahmed A. Selman

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