# Mahdi

### University of Waterloo

MATLAB Enthusiast.

Chemical Engineering Student; interested in computation and modelling.

Enjoys Snowboarding.

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Question

How can I make this code more efficient?

Hello, Because of the large number of differential equations I'm trying to solve, I would like to make this code more efficie...

6 years ago | 1 answer | 0

### 1

answerX and Y matrix of size:1x68.this code works well.but when command " plot(X,Y,'ro', x,y,'-b',xt,yt,'--g');" shifted outside for loop; plot for last value of xt and yt How to store all values of xt and yt outside for loop?

Change the the lines to: xt(i,:) = X0+(0.1*(max(X)-min(X))*[-1 0 1]); and yt(i,:) = y(k) + m(k)*(0.1*(max(X)-min(...

8 years ago | 0

Cubic spline interpolation with second derivative at ends as zero

Doesn't the <http://www.mathworks.com/help/matlab/ref/spline.html spline> function work?

8 years ago | 0

i want some links to basic matlab problem solving

The <http://www.mathworks.com/matlabcentral/cody/?s_tid=gn_mlc_cody cody> problems give some quick practice.

8 years ago | 0

| accepted

How i save the value of c in deach loop and sum these value after each value then using value in another eq outside loop??

Say E=3; for i=1:3 A(i)=x((i-1)*3+1); B(i)=x((i-1)*3+2); C(i)=x((i-1)*3+3); Z(i)=A*B+C*A; W=E-sum(C); end

8 years ago | 0

How do I stack many files together into one?

One way of doing this name='SpectraA' for i=1:5 #Let's say you have SpectraA1....SpectraA5 Filename=strcat(name, num2str(...

8 years ago | 0

matlab exe file to run as admin

Do you have the shortcut? You can right click --> Properties --> Location and find it. Even there, you can right click the short...

8 years ago | 0

what's the program mistake?

Try this? clear all clc; syms x A=[x 2 1;1 0 -x;5 1 x]; b=det(A) r=eval(solve(b==0))

8 years ago | 0

How to make loop and sum the result ??

for i=1:3 A(i)=x((i-1)*3+1); B(i)=x((i-1)*3+2); C(i)=x((i-1)*3+3); R(i)=A^2+B^3+A*c; end Summation=sum(C);

8 years ago | 0

| accepted

Vector indexing inefficiency question.

Have you looked at <http://www.mathworks.com/help/matlab/ref/perms.html perms> built-in function? I'm sure you can manipulate to...

8 years ago | 0

| accepted

I face the error of "In an assignment A(I) = B, the number of elements in B and I must be the same" when i want to create a loop a matrix. my simple short code given below, plz help me?

p(i) is one element, but you are trying to tell it to store multiple values, one of the following would fix your problem (Just r...

8 years ago | 0

| accepted

Extract a row of multiple files in loop

I didn't look through the whole code, but based on the error, try the following: line(i) =line(i)+Signal(pixel_line,:); ...

8 years ago | 0

| accepted

Reading specific Cell in Excel

Have you looked at the <http://www.mathworks.com/help/matlab/ref/xlsread.html xlsread> documentation? It tells you exactly how t...

8 years ago | 1

Extract xdata and ydata from hggroup

If you have the .fig file, you can just follow this <http://www.mathworks.com/matlabcentral/answers/100687-how-do-i-extract-data...

8 years ago | 0

How to make a vector where each element=5 and 100 elements long?

What you did produces a vector that starts at 1 and goes up by 5 till it reaches 100 elements. If that was your goal, then it's ...

8 years ago | 0

Question

Why is 10^5 more expensive than 10e5?

As Jan mentioned in this <http://www.mathworks.com/matlabcentral/answers/57638#comment_119764 post>, what's the reason behind it...

8 years ago | 1 answer | 1

### 1

answeri need to fix errors in interface

This line: filename('waad s.jpg') is not a valid code to put into MATLAB. I am not sure what you're trying to do, but th...

8 years ago | 0

change the number of digits after decimal point

You can use the <http://www.mathworks.com/help/matlab/ref/sprintf.html sprintf> or the <http://www.mathworks.com/help/matlab/ref...

8 years ago | 1

| accepted

plot multipe figures with diferents color

You can iterate through each point with a for loop ColoursToUse=['r' 'b' 'g' 'c'] figure(1) hold on for i=1:4 plot3(mx(...

8 years ago | 0

how can I direct a user to the script end script skipping intermediate?

You can easily just add an if statement for the code to only apply based on what you input into it. For example, let's say I hav...

8 years ago | 0

Generation of random numbers

I think what you're trying to do is done using randn, so that dd=(10^(4) - 10^(-4)).*randn(1000,1) + 10^(-4) hist(dd,100...

8 years ago | 0

| accepted

what 's different between axis square and axis equal in matlab ?

From this <http://www.mathworks.com/help/matlab/ref/axis.html page>: axis equal sets the aspect ratio so that the data units ...

8 years ago | 3

| accepted

I want to make a function with save option.

The problem is in the way you're handling the variables. Basically, the inputs to your function in this case are taken as variab...

8 years ago | 0

| accepted

How to use legend command

Is the loop still telling the figure to plot even if there isn't any data recorded? You have a few ways around it: The first...

8 years ago | 0

| accepted

How to plot multiple iterations on the same axes?

figure; hold on for i=1:length(s_x_index) f_value(i)=f_x # This is the value that you get from each iteration end plot(s_x...

8 years ago | 0

Convert a Roman numeral to its decimal equivalent for first ten roman numerals?

Have a look at this <http://www.mathworks.com/matlabcentral/fileexchange/26161-roman2num-and-num2roman--modern-roman-numerals fu...

8 years ago | 0

How May I import date/time from Excel?

Have you looked at this <http://www.mathworks.com/matlabcentral/newsreader/view_thread/284903 solution>?

8 years ago | 0

How come i get different output answers with the same matlab version, the same code installed on two different computers?

I am assuming that your problem is ill-conditioned or is very sensitive and depends greatly on the numbers from each step (or th...

8 years ago | 0

| accepted

how to change matrix dimensions?

Based on what you told me, let's say that the data for the years 1984-2009 is stored in matrix A, you would simply do: B=A(...

8 years ago | 0

| accepted

How to get image from axes in GUI matlab

After knowing which axes handle the image is loaded into, you can simple use the <http://www.mathworks.com/help/images/ref/getim...

8 years ago | 1