Position index
secMinIdx<-function(x)
{
infty<--10^20; #define this as a very small number;
n<-length(x);
if(n <2) return(NULL);
mysec<--infty; mymin<-x[1];
idx<-1; idx2<-NULL;
for(i in 2:n)
{
if(x[i] < mymin)
{
mysec<-mymin; idx2<-idx;
mymin<-x[i]; idx<-i;
}
else
{
if(x[i] < mysec)
{
mysec<-x[i]; idx2<-i;
}
}
}
return(idx2);
}