Index exceeds matrix dimensions.

[dorodeus78]

Hi!

I need a help, I am a beginner in matlab programming and I am trying to write a function to compute associative legendre funtions by recursive relations. I am getting this error message

??? Index exceeds matrix dimensions.

Error in ==> D:\Matlab\Pmbar_nm.m
On line 28 ==> Pbar(m) = u*sqrt((2*m+1)/(2*m))*Pbar(m-1,m-1);

I have typed the following code

function Pmbar_nm = Leg(phi,n_max,t)
%LEG copmutes the normalized associated legendre functions Pnm(t)by recurrence relation
if (nargin == 0)
phi = -6;
n_max = 18;
lambda = 39;
h = 0;
end;
%Initialize n_max
n_max = 180;

if n_max > 180, disp('Degree too large for the function, Upper summation bound too large!'), return, end;

GM = 3986004.418e8; % m^3/s^2
a_e = 6378136.46; % m
finv = 298.257223563; % flatenning

% We input geodetic coordinates phi,lambda in degrees
% We have to transform the geodetic coordinates to geocentric coordinates in radians
[X,Y,Z] = frgeod(a_e,finv,phi,lambda,h);
[lambda,phi_geoc,r] = cart2sph(X,Y,Z); % lambda and phi_geoc are now in radians
t = sin(phi_geoc); % phi_geoc is geocentric latitude

% Pbar computes the normalized associated legendre function on the diagonal
Pbar =zeros(n_max+3,1);
for m = 2:n_max
u= cos (phi_geoc)
Pbar(m) = u*sqrt((2*m+1)/(2*m))*Pbar(m-1,m-1);
end

% Computing the normalisation coefficients a_nm and b_nm
a_nm = zeros((n_max+3)*(n_max+4)/2,1);
b_nm = a_nm;
for m = 1:n_max+1
for n = m+1:n_max
s = loc(n+1)+m;
a_nm(s) = sqrt(((2*n+1)*(2*n-1))/((n-m)*(n+m)));
b_nm(s) = sqrt(((2*n+1)*(n+m-1)*(n-m-1))/((2*n-3)*(n+m)*(n-m)));
end
end
q = a_e/r;
Pmbar(n-1,m) = zeros(n_max+4,1);
Pmbar(t)= Pmbar(n-1,m);
for n = 2:n_max
for m = n_max:-1:2
Pmbar(n-1,m) = Pbar(t)/u^m *10^(-280);
end
Pmbar(t)= a_nm*q*t*Pmbar(n-1,m)-b_nm*q^2*Pmbar(n-2,m);
end
Pmbar(t)

I don't know what to do, please help me! thank you in advance.

dorodeus

 

[MikeyP]

Pbar is defined as a 1D vector.

Pbar =zeros(n_max+3,1);

In line 28 you reference it as a 2D matrix

... *Pbar(m-1,m-1);

M

--
Dr Michael F Platten

 

[dorodeus78]

Hi Dr Michael,

Thank you very much for your quick respose to my question. let me try to correct my mistake. Thanks,

dorodeus