URGENT variable name matlab help


by mathsgeek
Tags: matlab, urgent, variable
mathsgeek
mathsgeek is offline
#1
Oct2-09, 12:15 AM
P: 63
How do i change the variable, so it saves all the values, even if it must happen for 6 different variables name. This is because when i run it, it only saves the values for v_max when n=10 as this is the last iteration. How can i make all the values be saved. My coding is below:

radius=1:0.5:2.5;
total_flow_velocity=5

for n=5:1:10
v_max = (total_flow_velocity.*(1+n).*(1+(2.*n)))./((2.*pi)*((radius.*n).^2))
end

Thanks
Phys.Org News Partner Science news on Phys.org
Review: With Galaxy S5, Samsung proves less can be more
Making graphene in your kitchen
Study casts doubt on climate benefit of biofuels from corn residue
JeroenS
JeroenS is offline
#2
Oct2-09, 03:06 AM
P: 5
probably the best way is to store them in a vector. You define a vector called v_max with a length equal to the amout of values, in your case that is 6:

v_max=[1:6];

then you can store each value in one of the positions of the maxtrix like:

for n=5:1:10
v_max(1,n-4) = (total_flow_velocity.*(1+n).*(1+(2.*n)))./((2.*pi)*((radius.*n).^2))
end

I used n-4 to define column number 1 because you start with n=5. After that you can recall any value by typing:

v_max(1,1) .... v_max(1,6)

good luck!
mathsgeek
mathsgeek is offline
#3
Oct2-09, 03:34 AM
P: 63
ive tried it but i get the error "Subscripted assignment dimension mismatch." ? Also why did u do vmax=[1:6] because for each r value ive made it so i get an answer at each n value, so shouldnt the matrix be a 6x4?

ApexOfDE
ApexOfDE is offline
#4
Oct2-09, 08:00 AM
ApexOfDE's Avatar
P: 122

URGENT variable name matlab help


JeroenS' code has a mistake inside for loop. v_max(1,n-4) ==> indicate member (1, n-4) of array v_max. However, in the calculation, he forgot to delete the operator for array: (radius.*n). This operator (.*) will return an array radius multipled by n. So, in the left-side, you have 1 variable, not an array but in right side, there is an array. That's the reason matlab throws an error.

My code is:

vM = [];
j = 0;

radius = 1 : 0.5 : 2.5;
tfv = 5;

for n = 5 : 1 : 10
    j = j + 1;
    nR = 2 * pi * (radius * n).^2;
    vM(j, :) = (1 + n) * (1 + 2*n) * tfv ./ nR;
end
Hope this help.

p/s: i am totally confused when i read your code. There are many unnecessary parentheses and operators.
mathsgeek
mathsgeek is offline
#5
Oct2-09, 06:41 PM
P: 63
Thanks so much, yeh i don't know why i use so many brackets and that, buts it because im use to the calculator and have only been learning MATLAB for a few weeks now :P but im beginning to learn to use less brackets :P


Register to reply

Related Discussions
MATLAB - changing variable name with each iteration? Math & Science Software 16
Matlab: Use string variable as variable name Math & Science Software 5
MATLAB char array with variable names Math & Science Software 2
matlab user input variable name Math & Science Software 1
Stochashic variable result(Please verify) Urgent Calculus & Beyond Homework 0