[GRASS-stats] rgrass7 read/write SpatialPolygonsDataFrames errors

[Roger Bivand]

On Sat, 10 Oct 2015, Eduardo Diez wrote:

> This is what i got:
>
>> vinfo0 <- execGRASS("v.info", flags="c", map=zm.gnrl)INTEGER|cat
> INTEGER|ID
> INTEGER|GRIDCODE
> Displaying column types/names for database connection of layer <1>:
>
>
> And trying to read back the original polygon (without v.clean):
>
>> zm.fnl <- readVECT(zm.pol)Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings,  :
>  line 4 did not have 2 elements
>

This is coming from:

     G_message(_("Displaying column types/names for database connection of 
layer <%s>:"), field_opt);

line 134 in vector/v.info/print.c.

For me in nc_basic, for schools, I do not see the message with:

vinfo0 <- execGRASS("v.info", flags="c", map="schools", layer="1",
  intern=TRUE)

which is what is being used in vColumns. Is there an alternative to v.info 
that may be less error-prone?

Roger

>
>
>
>
> 2015-10-10 13:12 GMT-03:00 Roger Bivand <Roger.Bivand at nhh.no>:
>
>> On Sat, 10 Oct 2015, Eduardo Diez wrote:
>>
>> Apparently "v.info" through execGRASS is expecting the "layer" argument to
>>> be a string rather than an integer.
>>>
>>
>> Yes, please re-run with "1"; this resulted from GRASS6 to GRASS7
>> over-enthusiastic changing everything just for fun - this isn't the
>> problem. Run (assuming that zm.gnrl contains a character string):
>>
>> vinfo0 <- execGRASS("v.info", flags="c", map=zm.gnrl)
>>
>> My guess is that v.info is saying that this map is broken, or suffering
>> from something that vColumns does not know about.
>>
>> v.info -c map=
>>
>> should simply respond with "<storage type>|<name>" lines for the fields in
>> the layer. Here, its fourth line (unlike the first three) does not have two
>> elements (the type/name pairs).
>>
>> Does readVECT() work if you do not use v.clean? Is v.clean having a side
>> effect of causing v.info -c to "say" something else? How should the input
>> columns of the object to be cleaned be turned into output columns (simply
>> copy across the retained areas?)?
>>
>> Roger
>>
>>
>

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 91 00
e-mail: Roger.Bivand at nhh.no