Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

**--overwrite**- Allow output files to overwrite existing files
**--help**- Print usage summary
**--verbose**- Verbose module output
**--quiet**- Quiet module output
**--ui**- Force launching GUI dialog

**input**=*string[,**string*,...]**[required]**- Raster names of equally spaced time series.
**result_prefix**=*string***[required]**- Prefix for raster names of filterd X(t)
**coef_prefix**=*string***[required]**- Prefix for names of result raster (rasters of coefficients)
**timevar_prefix**=*string***[required]**- Prefix for names of result raster (rasters of time variables)
**freq**=*float[,**float*,...]**[required]**- List of frequencies for sin and cos functions

X(t) = B0 + B1*t + B2*sin(B1*t) + B3 * cos(B1*t) + ... + B{n-1}*sin(Bk*t) + Bn * cos(Bk*t) + e

where *X* is a raster time series, *t* is time (*t*
in *[0, pi]*), *sin(Fi*t)* and *cos(Fi*t)* are time
variables; *Fi* are user specifed frequencies; *e* is a error.

The module used r.mregression.series to find the regression coefficients
*Bi*, then it produces the fitted rasters series *X(t)*
using the coefficients.

So the module makes each output cell value a function of the values assigned to the corresponding cells in the time variable raster map series and the rasters of the coefficients.

*input* Raster names of equally spaced time series *X*

*result_prefix* Prefix for raster names of filterd *X(t)*

*coef_prefix* Prefix for names of result raster
(rasters of coefficients)

*timevar_prefix* Prefix for names of result raster
(rasters of time variables)

*freq* List of frequencies for sin and cos functions

The list of inputs for each cell (including NULLs) is passed to the
regression function. The functin compute the parameters over the
non-NULL values, producing a NULL result only if there aren't enough
non-NULL values for computing.
The regression coefficients *Bi* are stored in raster maps.
They can be used for construct more detail time series via the equation:

X(t) = B0 + B1*t + B2*sin(B1*t) + B3 * cos(B1*t) + ... + B{n-1}*sin(Bk*t) + Bn * cos(Bk*t) + e

To do that the user have to create time variables (*t*,
*sin(Fi*t)* and *cos(Fi*t)*) at desired time *T0*
and then use r.mapcalc to produce the *X(T0)*.

The maximum number of raster maps to be processed is limited by the
operating system. For example, both the hard and soft limits are
typically 1024. The soft limit can be changed with e.g. `ulimit -n
1500` (UNIX-based operating systems) but not higher than the hard
limit. If it is too low, you can as superuser add an entry in

/etc/security/limits.conf # <domain> <type> <item> <value> your_username hard nofile 1500

> g.mlist rast pattern="mod*", separator=',' mod2003_01_01,mod2003_01_09,...,mod2003_12_27

We use one year data, so we suppose the there is a half of sinusoid signal in the data (NDVI values icrease, then decrease usualy). So 01 jan is t0==0, 27 dec is tn==2*pi, there is a frequence 0.5 in the data (and there are more frequencies, for example 1.0 and 1.5).

Decompose the signal:

> maps = $(g.list rast pattern="mod*", separator=',') > r.series.decompose input=$maps coef_prefix="coef." \ timevar_prefix="dec." result_pref="res." \ freq=0.5,1.0,1.5

The command creates rasters of the coefficiens *coef.**:

coef.const coef.time coef.sin_fr0.5 coef.cos_fr0.5 coef.sin_fr1.0 coef.cos_fr1.0 coef.cos_fr1.5 coef.sin_fr1.5and rasters of fitted NDVI

res.mod2003_01_01 res.mod2003_01_09 ...

To compute NDVI for 03 jan we need: (1) find time *T* for 03 jan
(2) create time variables for 02 jan.

The length (in days) of the NDVI time series is 362, 03 jan
is the third day of the series, so *T* = *3 * (2*pi/362)*
radians. But r.mapcalc uses degrees for *sin()* and *cos()*
functions. So *T* = *3 * 360/362* degrees.

Create time variables:

r.mapcalc "T = 3.0 * 360.0/362.0" r.mapcalc "sin0.5 = sin(0.5*3.0*360.0/362.0)" r.mapcalc "cos0.5 = cos(0.5*3.0*360.0/362.0)" r.mapcalc "sin1 = sin(3.0*360.0/362.0)" r.mapcalc "cos1 = cos(3.0*360.0/362.0)" r.mapcalc "sin1.5 = sin(1.5*3.0*360.0/362.0)" r.mapcalc "cos1.5 = cos(1.5*3.0*360.0/362.0)"

Create NDVI for 03 jan:

r.mapcals "ndvi03jan = coef.const + coef.time*T +\ coef.sin_fr0.5*sin0.4 + coef.cos_fr0.5*cos0.5 +\ coef.sin_fr1.0*sin1 + coef.cos_fr1.0*cos1 +\ coef.sin_fr1.5*sin1.5 + coef.cos_fr1.5*cos1.5"

Available at: r.series.decompose source code (history)

Latest change: Monday Jan 30 19:52:26 2023 in commit: cac8d9d848299297977d1315b7e90cc3f7698730

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© 2003-2024 GRASS Development Team, GRASS GIS 8.3.3dev Reference Manual