Array indices must be positive integers or logical values.

Hi i have define the function

function y=triangle_basisn(phi,kk)

%[f,N,ra,k0,Z0,lambda] = parameter();

N=40

dftm=2.*pi./(N-1);

for jj = 1:N

Phi0(jj)=(jj-1).*dftm;

end

Phin=Phi0;

if ( phi >= Phin(kk-1) ) & ( phi <=Phin(kk))

y=(phi-Phin(kk-1))./dftm

elseif (phi >= Phin(kk) ) & (phi <=Phin(kk+1))

y=(Phin(kk+1)-phi)./dftm

else

y=0

end

end

When i call the funcrion i receive the message

Array indices must be positive integers or logical values.

i thni the problem is the tem kk-1 when kk=1 the matlab cant define zero index ?

there a way to ovecomne the problem ?

thank

George

Answer 1

[Cris LaPierre]

I can reproduce the error if I set kk=1. In this case, Phin(kk-1) becomes Phin(0), which is causing the error. In MATLAB, the index cannot be 0.

y=triangle_basisn(10,1)

N = 40

Array indices must be positive integers or logical values.

Error in solution>triangle_basisn (line 11)
if ( phi >= Phin(kk-1) ) & ( phi <=Phin(kk))

function   y=triangle_basisn(phi,kk)
%[f,N,ra,k0,Z0,lambda] = parameter();
N=40
dftm=2.*pi./(N-1);
for jj = 1:N
    Phi0(jj)=(jj-1).*dftm; 
end
Phin=Phi0;
if ( phi   >=  Phin(kk-1)  ) & ( phi <=Phin(kk))
    y=(phi-Phin(kk-1))./dftm
elseif (phi  >=  Phin(kk)  ) &  (phi <=Phin(kk+1))
    y=(Phin(kk+1)-phi)./dftm
else
    y=0
end
end

One way to overcome this is to define an if condition for when kk=1. What the corresponding code does would be up to you, but it would prevent the error. Here's an example:

if kk==1

y=phi;

elseif( phi >= Phin(kk-1) ) & ( phi <=Phin(kk))

y=(phi-Phin(kk-1))./dftm

elseif (phi >= Phin(kk) ) & (phi <=Phin(kk+1))

y=(Phin(kk+1)-phi)./dftm

else

y=0

end