Annual integration of NDVI

[i-m-amit]

@12rambau what is your thought on the integration of NDVI values into an annual series?

def daily2monthly2annual(year):
    months = ee.List.sequence(1,12)
    ndvi_coll_ann = ndvi_collecion.filter(ee.Filter.calendarRange(year, field = 'year'))
    
    img_coll= ee.ImageCollection.fromImages(
        months.map(lambda month:
                  ndvi_coll_ann \
                  .filter(ee.Filter.calendarRange(month, field = 'month')) \
                  .reduce(ee.Reducer.mean()))
        
    )
    img_coll = img_coll \
        .reduce(ee.Reducer.mean()) \
        .rename('ndvi') \
        .addBands(ee.Image().constant(year).rename('year')) \
        .set('year',year)
    return img_coll

def int_yearly_ndvi(ndvi_coll, start, end):
    """Function to integrate observed NDVI datasets at the annual level"""
    
    years = ee.List.sequence(start, end)
    ndvi_collecion = ndvi_coll
    img_coll = ee.ImageCollection.fromImages(
        years.map(daily2monthly2annual)
    )
   
    return img_coll

[12rambau]

seems nice, Is it compatible with the rest of the app ? (i've tried something similar at some point and It was raising errors in the rest of the process)

[i-m-amit]

You just forgot to cast the constant image to float.

[12rambau]

from functools import partial 

def daily2monthly2annual(year, ndvi_collection):
    months = ee.List.sequence(1,12)
    ndvi_coll_ann = ndvi_collecion.filter(ee.Filter.calendarRange(year, field = 'year'))
    
    img_coll= ee.ImageCollection.fromImages(
        months.map(lambda month:
                  ndvi_coll_ann \
                  .filter(ee.Filter.calendarRange(month, field = 'month')) \
                  .reduce(ee.Reducer.mean()))
        
    )
    img_coll = img_coll \
        .reduce(ee.Reducer.mean()) \
        .rename('ndvi') \
        .addBands(ee.Image().constant(year).float().rename('year')) \ # need to cast the constant image to float.
        .set('year',year)
    return img_coll

def int_yearly_ndvi(ndvi_coll, start, end):
    """Function to integrate observed NDVI datasets at the annual level"""
    
    years = ee.List.sequence(start, end)
## need to change the scope of this varibale to global
    #global ndvi_collecion
    #ndvi_collecion = ndvi_coll
    img_coll = ee.ImageCollection.fromImages(
        years.map(partial(daily2monthly2annual, ndvi_collection=ndvi_coll)
    )
   
    return img_coll

I think using partial should do the trick
I case you're interested : https://stackoverflow.com/questions/15331726/how-does-functools-partial-do-what-it-does

[i-m-amit]

Not working.
It returns a value error: ValueError: Function has keyword-only parameters or annotations, use inspect.signature() API which can support them

[i-m-amit]

Following is working after nesting the function inside the parent.

def int_yearly_ndvi(ndvi_coll, start, end):
    """Function to integrate observed NDVI datasets at the annual level"""
    def daily_to_monthly_to_annual(year):
        months = ee.List.sequence(1,12)
        ndvi_collection = ndvi_coll
        ndvi_coll_ann = ndvi_collection.filter(ee.Filter.calendarRange(year, field = 'year'))
    
        img_coll= ee.ImageCollection.fromImages(
        months.map(lambda month:
                  ndvi_coll_ann \
                  .filter(ee.Filter.calendarRange(month, field = 'month')) \
                  .reduce(ee.Reducer.mean()))
        
        )
        img_coll = img_coll \
            .reduce(ee.Reducer.mean()) \
            .rename('ndvi') \
            .addBands(ee.Image().constant(year).float().rename('year')) \
            .set('year',year)
        return img_coll
    years = ee.List.sequence(start, end)
    img_coll = ee.ImageCollection.fromImages(
        years.map(daily_to_monthly_to_annual)
    )
   
    return img_coll

[12rambau]

normally you shouldn't do it this way but maybe it's a GEE python API limitation. keep it that way and we'll modify it afterward if neededd

[i-m-amit]

It returns an error if there no image available in any of the months.
instead of months = ee.List.sequence(1,12) this hardcoded list, We need to get the month numbers dynamically where images are available.

[12rambau]

nice catch