[GRASS-user] r.mapcalc and polygons

GRASS GRASS user
1

Hi! all,
I wish to perform r.mapcalc algebra for an area bound by certain polygons in a vector file. How to do this?
Are there any correlation and anova expressions for r.mapcalc. I would like them to use for, kindly help me how to put these expressions if there is no such things, for eg, Corr(ma1, map2, bound by polygon a).

thanks!
ambrish

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2

ambrish dhaka wrote:

Hi! all,
I wish to perform r.mapcalc algebra for an area bound by certain polygons in a vector file. How to do this?

Easiest would probably be to use a raster MASK:
1- convert the vector (“polygon” ) to a raster with v.to.rast
2- define this new raster as a mask with r.mask
3- run your r.mapcalc expression

–
Micha

Are there any correlation and anova expressions for r.mapcalc. I would like them to use for, kindly help me how to put these expressions if there is no such things, for eg, Corr(ma1, map2, bound by polygon a).

thanks!
ambrish

3

ambrish dhaka wrote:

And, how to write correlation expression for two maps. Need help!
Ambrish

I’m not sure what you mean by “correlation expression”. Perhaps a more specific question will get a better response from the list.

4

On 16/03/09 12:32, Micha Silver wrote:

ambrish dhaka wrote:

And, how to write correlation expression for two maps.

There are no ready-made functions for correlation in r.mapcalc, but you can use r.covar.

Moritz