Hi list
I have a vector, which are remotely sensed chlorophyll values for a certain
pixel in 11 years, then i have a flag or label vector (t_max) that consists
of 0 and 1, which tells me where i have the annual peak (one per year, then
eleven 1 and all the rest are 0).
I'm interested in extracting the date in which the bloom beggins. For that
matter I'm using a threshold of 5% above the median of the whole series.
I need to go over the chlorophyll data vector (cla) and every time I find
the yearly maximum value (where t_max == 1), i need to go backwards in cla
as many time steps as needed untill I cross the threshold (5% over the
median of cl)... once i crossed that threshold, i need to be sure that at
least for 2 time steps, the value of cla keeps going down (it's below the
threshold)... once that condition is met, i want to get the first position
where cla is higher than that threshold...
that would be the phytoplankton bloom starting date...
This is more or less what i was trying, but it does not work and i'm
stuck... can you please help me??
cla<- ts of 506 values (every 46 values, i have one year)
t_max<- vector of 0 & 1; 1 where the yearly cla max occurs (11 ones & all
rest 0)
threshold = 0.05*median(cla)+median(cla)
for ( t in 1:length(t_max) ) {
if ( t_max[t] == 0 )
{
next;
} else {
if ( (cla[t-1] < threshold) && (cla[t-2)] < threshold) )
{
return which(cla[t])
}
}
}
Thanks a lot in advance!! :)
Vero
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