Nikos Alexandris:
Hi devs,
and advanced users. Has anyone performed, or has plans to
implement,
non-linear (multi-) regression in GRASS (not through R, of course)?
Markus Metz:
If it is raster based, you can use r.regression.multi to perform
non-linear (multi-) regression in GRASS. It depends on what you mean
with non-linear. E.g. if you want to perform a second-order multiple
regression with 2 predictors, the formula is in R syntax
y ~ x1 + x2 + x1 * x2 + x1 * x1 + x2 * x2
You can calculate the terms x1 * x2, x1 * x1, x2 * x2 with r.mapcalc
and feed everything to r.regression.multi.
logarithmic:
y ~ log(x1)
r.mapcalc "logx1 = log(x1)"
exponential:
y ~ exp(x1)
r.mapcalc "expx1 = exp(x1)"
A combination of say a 4th-order polynomial with exponential
components and 10 predictors could be constructed accordingly.
Speechless. Nikos
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