关于matlab函数的between函数

Question

% function amat=event_hyp(seis,t,x,0.4,700,v,1,3)

v=2000;
dx=10;
dt=.004;%basic model parameters2
x=0:dx:2000;%x axis3
t=0:dt:2;%t axis4
seis=zeros(length(t),length(x));
% seis=event_hyp(seis,t,x,.4,700,v,1,3);
flag=1;aper=3;
tnot=0.4;
xnot=700;
amat=zeros(2000,2000);
amp=1;

% if(nargin<8)
% flag=3;
% end
% if(nargin < 9 )
% aper = inf;
% end

v=v/2;

%loop over columns
[nsamp,nc]=size(amat);

dt=t(2)-t(1);
tmin=t(1);
for k=1:nc
xoff=x(k)-xnot;
if(abs(xoff) < aper)
tk = sqrt(tnot^2+(xoff/v)^2);
a=amp;
if(flag==2)
a = tnota/tk;
elseif(flag==3)
a = tnota/(tk^1.5);
elseif(flag==4)
a = tnota/(tktk);
end
ik=(tk-tmin)/dt+1;
if( between(1,nsamp,ik) )
ik1=floor(ik);
ik2=ceil(ik);
if(ik1==ik2)
amat(ik1,k)=amat(ik1,k)+a;
else
amat(ik1,k)=amat(ik1,k)+a*(ik-ik2)/(ik1-ik2);
amat(ik2,k)=amat(ik2,k)+a*(ik-ik1)/(ik2-ik1);
end
end
end
end
figure(1);imagesc(amat);colormap gray

在这段代码里面的between用法是不是有些不正确，因为是学习代码所以不太懂，问问大噶