Description Usage Arguments Details Author(s) See Also Examples
The function PeriodAnomaly compute the anomaly map on a given period of time.
1 2 3 4 5 |
ndvidirectory |
path to the ndvi images folder (GeoTIFF files). |
region |
name of the region, same as in the name of the ndvi images. |
Ystart |
starting year of the analysis (in four-digit format). |
Yend |
ending year of the analysis (in four-digit format). |
period |
vector containing the period to focus. |
outname |
prefix of the name of the files where the anomaly maps are saved. |
outext |
extension of the created maps. |
xlim |
a two dimensions vector containing the longitude limits of the area of interest. |
ylim |
a two dimensions vector containing the latitude limits of the area of interest. |
type |
type of nomenclature followed by the NDVI images : "VITO_CLIP", "VITO_VGT" or "GIMMS" (see details for more information). |
shapefile |
name of the shape/kml file with objects (points or polygons) to be displayed on the maps. |
shapedir |
path to the shape/kml file. |
shapeext |
extension of the shape/kml file : "shp" for a Esri shapefile or "kml" for a kml file from Google earth . |
label |
name of the label of the points to be displayed on the map. |
pal |
name of the palette of colors used to make the map from the package RColorBrewer. |
Computing seasonal anomaly put the emphasis on the difference of NDVI signal for a given period, often the growing season.
For each year, the mean of the NDVI is computed over the given period.
Then, the global mean over the year is calculated for this period.
Anomaly maps comes from the difference between the annual mean of the period and the global mean.
If the difference is positive, it means the season was greener than usual.
On the contrary, if it is negative, the season was worst than normal.
These values are computed for each pixel and the output maps of anomaly are coded with 16 bits, with a factor of 10000 to get value between -10000 and 10000.
The map of global mean over the years for the given season is also saved in the same way (a factor of 10000 is applied) as well as the standard deviation map.
More about the variable type :
type = GIMMS : nomenclature from Global Land Cover Facility
[RE][YY][MMM][DDD].[SAT]-VIg.tif
RE : identifies the continent (AF for Africa,AZ for Australia and New Zealand, EA for Eurasia, NA for North America and SA for South America and Central America)
YY : the two last digits of the year
MMM : three-letter abbreviation of the month
DDD : identifies the composite period, 15a denotes the days 1-15 of the month, and 15b denotes the days from 16 to the end of the month.
SAT : identifies the satellite, NOAA-7, 9, 11, 14, 16, or 17 from which the data originated.
type = VITO_VGT : FreeVGT VITO's nomenclature
NDV_[YYYYMMDD]_[REGION]_Extract.tif
YYYY : identifies the year (four digits)
MM : identifies the months (two digits)
DD : identifies the date of the period : "01", "11" or "21" (10-day composite).
REGION : idendifies the region selected while extracting maps
type = VITO_CLIP : nomenclature after clipping the images in a particular region.
[REGION][YYYY]M[MM]P[D].tif
REGION : the region as entered while clipping data.
YYYY : identifies the year (four digits)
MM : identifies the months (two digits)
D : identifies the period (0, 1 or 2).
Romain Frelat and Bruno Gerard
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | #local variables
ndvidirectory=paste(system.file("extdata/VITO_Mzimba",
package="ndvits"), "/", sep="")
region="Mzimba"
Ystart=2004
Yend=2009
period=2:18
#executing PeriodAnomaly
PeriodAnomaly(ndvidirectory, region, Ystart, Yend,
period = period, outname="Mzimba", outext="show")
#adding points to the map
shape="SLP_Mzimba"
shapedir=paste(system.file("extdata/shape", package="ndvits"),
"/", sep="")
PeriodAnomaly(ndvidirectory, region, Ystart, Yend,
period = period, outname="Mzimba", outext="show",
shapefile=shape, shapedir=shapedir, label="Village")
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