I have done similar work, for native computer R or matlab, I prefer S-G method (Savitzky-Golay filtering). It can effectively reduce the noise of cloudy day and low quality day. Code see below:

library(terra) library(signal) library(zoo) mvclist = list.files(path = "./MODNDVI1kmon/", pattern = ".tif$") mvcdir = paste0("./MODNDVI1kmon/", mvclist) mvcdata = rast(mvcdir) sg_fun = function(x){   v = as.vector(x)   z = zoo::na.aggregate(v)    #replace NA with mean value   mod_ts = ts(z, start = c(2001,1), end = c(2020,12), frequency = 12)      x = signal::sgolayfilt(mod_ts, p=3, n=9, ts=10) } mod_filtered = app(mvcdata, sg_fun, cores=8) plot(mod_filtered) mod_name = seq.Date(as.Date("2001-01-01"), as.Date("2020-12-31"), "month") names(mod_filtered) = mod_name writeRaster(mod_filtered, filename = "./mod1k_SGfilter/mod1k_SGfilter2020.tif", names=mod_filtered@ptr[["names"]])

Longhao Wang thank you very much for your suggestion i will try this and if i face any problem i will discuss it with you. Thanks again

Katarzyna Ewa Lewińska thanks responding. Actually i need daily NDVI and other vegetation indices but i can't find the daily composites. If you can share the link it will be helpful for me.

thanks

Hi Adeel Ahmad Nadeem, were you able to do it? I am trying to do the same now. I want to convert the pre-existing MODIS 16-day 250m NDVI information into a daily value. But I am also having some issues.

Appreciate it if you could share your experience and codes if any.

Thanks