filter_top: Filter top NDVI
In irg: Instantaneous Rate of Green Up

Description Usage Arguments Details Value See Also Examples

Using upper quantile (default = 0.925) of multi-year MODIS data, determine the top NDVI for each id.

1	filter_top(DT, probs = 0.925, id = "id")

`DT`	data.table of NDVI time series
`probs`	quantile probability to determine top. default is 0.925.
`id`	id column. default is 'id'. See details.

The id argument is used to split between sampling units. This may be a point id, polygon id, pixel id, etc. depending on your analysis.

filtered data.table with appended 'top' column of each id's top (quantile) NDVI value.

Other filter: filter_ndvi(), filter_qa(), filter_roll(), filter_winter()

# Load data.table
library(data.table)

# Read example data
ndvi <- fread(system.file("extdata", "sampled-ndvi-MODIS-MOD13Q1.csv", package = "irg"))

filter_qa(ndvi, ndvi = 'NDVI', qa = 'SummaryQA', good = c(0, 1))
filter_winter(ndvi, probs = 0.025, limits = c(60L, 300L), doy = 'DayOfYear', id = 'id')
filter_roll(ndvi, window = 3L, id = 'id')
filter_top(ndvi, probs = 0.925, id = 'id')