How to call a concrete number of a vector inside a function

Hi,

I have a position vector: x= [ 1 2 3 4 5 6 7] and an area vector A= [10 11 12 13 14 15]

I am trying to create a function called:

function [M] = Area_jumps (A1, A2,  c1, c2, rho1, rho2, x1, s) 
a  = A2/A1.*rho1.*c1/(rho2.*c1);
        t1 = s*x1./c1;
        t2 = s*x1./c2;
        
        M  = [-exp(-t1), -exp(t1),    +exp(-t2),     +exp(t2);
             -exp(-t1), +exp(t1), +a.*exp(-t2), -a.*exp(t2)];
end

% (where c is the speed of sound and rho is the density)

A1 and A2 represent the position, 1 and 2. But I want to do this for the 5th first position of the vector.

How can I do this?

Thank you

Answer 1

[Steven Lord]

It's not completely clear to me how the variables A1, A2, and x1 in your function are related to your A and x vectors. It's also not clear what "the 5th first position of the vector" means.

But taking an educated guess at where the problem lies, you may want to use element-wise division between A2 and A1.

A2 = 10:16;
A1 = 1:7;
sol1 = A2./A1 % sol1(k) is A2(k) divided by A1(k)
sol2 = A2/A1 % least-squares solution to sol2*A1 = A2, so a scalar

[Marina Fargas Canas]

Hi, thanks for answering. I'm sorry if I didn't explain myself properly. It is a bit difficult to explain.

A1 would represent the area in the position 1 and A2 in the position 2. But I need this to be changing until when A1= 13 and A2=14. The value x will be from 1 to 5. Also move 5 positions.

I thought on creating a loop that it looked like this:

function [M]= Area_Jump(A,c,rho,x,s,m)
        p = [1:m+3];
        k = p+1;
        
        a  = A(k)/A(p).*rho(p).*c(p)/(rho(k).*c(p));
        t1 = s*x(p)./c(p);
        t2 = s*x(p)./c(k);
        
        M  = [-exp(-t1), -exp(t1),    +exp(-t2),     +exp(t2);
             -exp(-t1), +exp(t1), +a.*exp(-t2), -a.*exp(t2)];
end

m = 2 but is defined in the main function

[Steven Lord]

A = 10:15;
m = 2;
p = 1:m+3;
k = p+1;

I think this is what you're looking for.

ratio = A(k)./A(p) % Note the ./ instead of /

[Marina Fargas Canas]

I have defined the vector A, x, c, rho in another function, this why I have them in the inputs. The vectors are not the ones I wrote they are a bit more complex. They are:

   x= [0; 0.0858; xm11; xm12; xm13; xm14; xm15; 0.0282; 0.2524; xm21;  
       xm22; xm23; xm24; xm25; 0.0424; 0.1787; 0.059;];
   
   A = [Ax1 A_ch1 Ax2 Ax3 A_ch2 Ax4 Ax5];  
   %A_ch1 and A_ch2 have been calculated previously
   
   c = [c1 cm c1 c2 c2]; 
   rho = [rho1 rhom rho1 rho2 rho2];
   
  %cm and rhom have been also calculated before. 
  
  

When I try to see the values of M it doesn't give me results and I don't understand why. Shall I store the values of M? shall I make a loop?

I am a bit lost with this.

At the end I want the Matrix M with all the numbers of the loop.