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r.mregression.series - Calculates multiple regression between time series: Y = b1*X1 + ... + bn*Xn.


raster, statistics, regression


r.mregression.series --help
r.mregression.series samples=string result_prefix=string [--overwrite] [--help] [--verbose] [--quiet] [--ui]


Allow output files to overwrite existing files
Print usage summary
Verbose module output
Quiet module output
Force launching GUI dialog


samples=string [required]
File contains list of input and output rasters
result_prefix=string [required]
Prefix for names of result raster (rasters of regression coefficients)

Table of contents


r.mregression.series is a module to calculate multiple linear regression parameters between several time series, e.g. NDVI and elevation, precipitation. It uses the python-statmodels package.

The module makes each output cell value a function of the values assigned to the corresponding cells in the input raster map series.


The module assumes a simple linear regression of the form
    Y = b1 * X1 + b2 * X2 + ... + bn * Xn 


The number of predictor variables (X maps) needs to be the same in each (time) series (see examples below). If the different time series have irregular time intervals, NULL raster maps can be inserted into time series to make time intervals equal.

The list of inputs for each cell (including NULLs) is passed to the regression function. The function computes the parameters over the non-NULL values, producing a NULL result only if there aren't enough non-NULL values for computing.


The most important paramether is samples; it provides the list of X and Y maps. The parameter is the name of csv file of the next structure: the first line is a header, other lines provide names of the X and Y maps. The header contains the names of the input and output variables.

For example the csv file for regression between NDVI and (elevation, precipitation)

    NDVI = b1*Elevation + b2*Precipitation 
could be the next file:
"ndvi_t" are names of the NDVI rasters, "precip_t" are names of precipitation rasters. The names of the first and the second predictor variables are "elevation" and "precipitation" accordingly.

The second paramether is result_prefix. It is used for construction of the coefficient names. For example if result_prefix="coef.", the names of the regression coefficients will be "coef.elevation" and "coef.precipitation".

r.mregression.series samples=settings result_prefix="coef."

If the regression model includes the intercept

    NDVI = b0 + b1*Elevation + b2*Precipitation 
then the constant map should be used:
r.mapcalc "ones = 1.0"
and the csv file is:
Then the command
r.mregression.series samples=settings result_prefix="coef."
produces three raster maps: "coef.offset", "coef.elevation", "coef.precipitation".


We create test data for the example. Suppose we have five Y maps and 5 pairs of predictor X = (x1, x2) maps.

Create X variables (random numbers):

r.mapcalc -s "x11 = rand(0, 20)"
r.mapcalc -s "x21 = rand(0, 20)"
r.mapcalc -s "x31 = rand(0, 20)"
r.mapcalc -s "x41 = rand(0, 20)"
r.mapcalc -s "x51 = rand(0, 20)"
r.mapcalc -s "x12 = rand(0, 20)"
r.mapcalc -s "x22 = rand(0, 20)"
r.mapcalc -s "x32 = rand(0, 20)"
r.mapcalc -s "x42 = rand(0, 20)"
r.mapcalc -s "x52 = rand(0, 20)"

Create constant raster for the intercept:

r.mapcalc  "ones = 1.0"

Suppose Y is a linear function of x1 and x2 variables plus a random error. (For testing purposes we assume that Y = 12 + 5*x1 + 3*x2). Create 5 Y rasters:

r.mapcalc -s "y1 = 12 + 5* x11 + 3*x12 + rand(0, 4)"
r.mapcalc -s "y2 = 12 + 5* x21 + 3*x22 + rand(0, 4)"
r.mapcalc -s "y3 = 12 + 5* x31 + 3*x32 + rand(0, 4)"
r.mapcalc -s "y4 = 12 + 5* x41 + 3*x42 + rand(0, 4)"
r.mapcalc -s "y5 = 12 + 5* x51 + 3*x52 + rand(0, 4)"

So we have five test rasters Y and X. Forget for a moment that we know the function and try to find the coeffitients.

Create samples csv file:

echo "y,bias,x1,x2
y5,ones,x51,x52" > settings.csv

Run the command

r.mregression.series samples=settings.csv result_prefix="coef."

Three raster maps will be created: "coef.bias", "coef.x1", "coef.x2". This rasters contains the fitted coefitients.


r.regression.series, r.series, r.regression.line, g.list, g.region


Dmitry Kolesov

Last changed: $Date: 2016-06-14 21:12:29 +0200 (Tue, 14 Jun 2016) $


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

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