Index in position 2 exceeds array bounds (must not exceed 25).

function[spl] = tryal2(f,P,t) 
if f == 40
    w = 2*pi*f;
    A = 10;
end
c = 343;
x = [0:.5:11];
y = [0:.5:15];
k = w/c;
[xx,yy]= meshgrid(x,y);
H = sqrt((xx-0).^2)+(yy-9).^2;
Lx = length(x);
Ly = length(y);
phasor = zeros(Lx,Ly);
Meanpressure = zeros(Lx,Ly);
spl = zeros(Lx,Ly);
for a=1:Lx
    for b=1:Ly
      phasor(a,b) = ((A+P)./H(a,b))*exp(1j*((w*t)-((w/c)*H(a,b))));
      Meanpressure(a,b) = sqrt(0.5*phasor(a,b)*conj(phasor(a,b)));
      spl(a,b)= 20*log10(Meanpressure(a,b)/(20*10^(-6))); 
    end 
end
    figure 
surf(xx,yy,spl)

The error occurs in phasor(a,b) = ((A+P)./H(a,b))*exp(1j*((w*t)-((w/c)*H(a,b)))); i am confused what i am doing wrong I need a grid by 11 by 14 but i only get answers if x and y martixes are the same.

Answer 1

[Geoff Hayes]

benjamin - isn't H of length Lx (or Ly since identical) and is an array? Treating it like a matrix as H(a,b) would then lead to this error. Note how

H = sqrt((xx-0).^2)+(yy-9).^2;

and so is not a matrix since xx and yy are arrays.

[benjamin chong]

So what do I need to do to fix it

[Geoff Hayes]

well either make H a matrix or just grab H(b) on each iteration. to be honest i don't know enough about your code (i.e. what it does) to tell you what to do.

[Geoff Hayes]

Benjamin - please provide the inputs to your function. What is f? What are P and t?

Also, please further the conversation by adding comments and not creating answers.

Answer 2

[benjamin chong]

if i run the code with

x = (1:h:15)
y = (1:h:15)

i get

if i run the code with

x =[1:h:12]
y =[1:h:15]

then i get the error

Error in tryal1 (line 39)
      phasor(a,b) = ((A+P)./H(a,b))*exp(1j*((w*t)-((w/c)*H(a,b))));

Answer 3

[benjamin chong]

my code is to plot the Sound pressure leve in DB on a meshgrid but my dimensions of the grid are 11 by 14 but the formula on line 39 wont work