[Bfast-commits] FW: Running bfast on raster bricks

[Polyanne Aguiar]

Hello,

 

I am using the bfast in my jobs. But, I am attempting run the bfastmonitor
on a raster brick (time serie MODIS EVI), I not get.

I followed the script proposed by you in this forum. But I did not succeed.

 

Following is the script used:

 

############################################################################
####

 

## TUTORIAL for processing raster bricks (satellite image time series of
16-day NDVI images)

 

file<- brick("MT_micro.tif", native, package="raster")

file

 

## helper function for the calc function 

xbfast <- function(file) {

        ndvi <- ts(file, frequency=23, start=c(2000,9))

        result <- bfast(ndvi, season="harmonic", max.iter=1, breaks=2)

        return(cbind(result$Magnitude,result$Time)) ## save magnitude and
time of the biggest break 

        }

 

## apply on a single pixel for testing

pixel <- as.vector(file[50])

ndvi <- ts(pixel, frequency=23, start=c(2000,9))

plot(ndvi)

result <- bfast(ndvi, season="harmonic", max.iter=1, breaks=2)

plot(result)

 

 

## apply on a single pixel using the xbfast function 

output <- xbfast(pixel)

output

  

 

## optimise function that takes into account the percentage of NA's within a
time series 

bfastfun <- function(y) {

        percNA <- apply(y, 1, FUN=function(x) (sum(is.na(x))/length(x)) ) ##
checks the percentage of NA's with the time series

        i <- (percNA<0.2)

        res <- matrix(NA, length(i), 2)

        if (sum(i) > 0) {

                 res[i,] <- t(apply(y[i,], 1, xbfast))

         }

        res

}

 

##apply on the full satellite image time series 

magntime <- calc(data, fun=bfastfun)

layerNames(magntime) <- c("Magnitude", "Time of biggest Break")

plot(magntime)

 

## two rasters are returned: i.e. the magnitude and time of the biggest
break ## WARNING: this is requires some time :-).

 

############################################################################
###################

 

Thanks,

 

 

Polyanne Aguiar dos Santos

Master in Applied Ecology - UFLA

Specialist in Environmental Management - UNISAM

Biologist - ESFA

Phone: +55 35 9178 3275

Skype: polyanne.aguiar

 

cid:image001.png at 01CDF3FB.781F9910

 

 

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