[STATSGRASS] isolines [solved]

[Poizot Emmanuel]

Tim Michelsen wrote:

>>On Mon, 28 Feb 2005, Tim Michelsen wrote:
>>    
>>
>>>>GRASS has limited support for TINs, you would have to extract values at
>>>>the nodes (v.in.ogr? -> vector points), interpolate to a raster map
>>>>using splines (v.surf.rst), then create vector isolines with r.contour.
>>>>        
>>>>
>>>Do you know any R package that might be able to do the job?
>>>      
>>>
>>No direct route from points to contours without interpolation in R. The
>>nearest I can see would be to use GMT's pscontour, inputting an ASCII xyz
>>file, and dumping the contour line output to file.
>>    
>>
>Finally I used contour() in R native to achive it.
>
>But does anyone know how to plot gradient arrows that demonstrate flow 
>streams?
>E. g. from the higher valued isoline to the lower valued.
>
>Thanks and greetings,
>Tim
>
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>
>  
>
Hi,

you can use arrow.plot from fields package:

arrow.plot(a1, a2, u = NA, v = NA, arrow.ex = 0.05,

          xpd = TRUE, true.angle = FALSE, ...)

Regards


Emmanuel Poizot