Doing Attached Calculation in Matlab

[intel2]

how can someone do the attach calculation in Matlab?

 

[shoehorn]

Read the documentation. The Matlab getting started guide is particularly good, and will teach you how to perform calculations like this and more.

 

[intel2]

i went through it but i couldn't get to work.. this is what i did:

for i = 0 : 100
for j = 1 : 101


dme = (sum (sum ((i/j)^ 2)+log(sqrt(j))));
end
end

 

[intel2]

how about this

for i = 0 : 100
for j = 1 : 101
x= (i/j)^2;
y = (j)^.5;
end
end


F = (sum (x)+log(y))

but the answer is not consistent with the mathcad ansr

 

[shoehorn]

There are a couple of important things to note.

Firstly, Mathcad is an infamously flaky piece of software. Use it only if you have absolutely no alternative.


Secondly, the answer you've got from Mathcad is incorrect. The actual result of the summation you've given is

$$\sum_{i=0}^{100} \sum_{j=1}^{101} \left[ \left(\frac{i}{j}\right)^2 + \log\sqrt{j} \right] \approx 571831.873$$

You can verify this using Mathematica, Maple, Matlab, or your own C/C++/Python code. Again let me stress: Mathcad is absolutely atrocious software. I've seen the source, and it's not pretty. Avoid it like the plague.


Thirdly, to evaluate the sum in Matlab you can do something like the following:

% First declare and initialize a dummy variable
x = 0;

% Now perform the summation:
for i = 0:100
for j = 1:101
x = x + (i / j)^2 + log(sqrt(j));
end
end

This should leave you with the variable x holding the result. Note that this is neither a particularly efficient nor elegant way of computing such a sum.

 

[Emreth]

Actually the mathcad result is correct. In matlab, log means ln, log10 means log.The answer shoehorn gives is for ln.
so the code is
% First declare and initialize a dummy variable
x = 0;

% Now perform the summation:
for i = 0:100
for j = 1:101
x = x + (i / j)^2 + log10(sqrt(j));
end
end

 

[intel2]

Thank you to shoehorn and to Emreth ..

 

[intel2]

since we r in the topic; how can i plot the attach equation between [-4,4] with a 0.001 interval using matlab

thanks in advance

 

[Emreth]

read the help files, this is quite trivial.

for i=1:3000
x(i)=-4+i/1000;
y(i)=-x^2-4*x-2;
end
for i=3000:5000
x(i)=-4+i/1000;
y(i)=abs(x);
end
for i=5000:8000
x(i)=-4+i/1000;
y(i)=2-exp(sqrt(x-1));
end
plot(x,y);

 

[intel2]

Tip of the Hat to Emreth ..

the way u wrote x(i) ,, is smart... once again thanks