drop layer/band from SpatialGridDataFrame

I have a SpatialGridDataFrame with 325 variables in the @ data slot. I want to drop the first layer. Seems simple enough. Any help? Thanks, Andy

str(monthly.sp)

Formal class 'SpatialGridDataFrame' [package "sp"] with 6 slots
?..@ data ? ? ? :'data.frame': 8060 obs. of ?325 variables:
?.. ..$ values: num [1:8060] 127.5 31.9 127.5 127.5 231.1 ...
?.. ..$ values: num [1:8060] 127.5 31.9 127.5 127.5 231.1 ...
?.. and so on

-----Original Message-----
From: Michael Sumner [mailto:mdsumner at gmail.com]
Sent: Monday, August 09, 2010 11:28 PM
To: Andy Bunn
Cc: r-sig-geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] drop layer/band from SpatialGridDataFrame

Do you mean "layer" as in the first column in the data.frame?

Does this do what you want?  The negative index means "everything but
these indexes".

monthly.sp <- monthly.sp[,-1]

On Tue, Aug 10, 2010 at 12:40 PM, Andy Bunn <Andy.Bunn at wwu.edu> wrote:

I have a SpatialGridDataFrame with 325 variables in the @ data slot.

I want to drop the first layer. Seems simple enough. Any help? Thanks,
Andy

str(monthly.sp)

Formal class 'SpatialGridDataFrame' [package "sp"] with 6 slots
?..@ data ? ? ? :'data.frame': 8060 obs. of ?325 variables:
?.. ..$ values: num [1:8060] 127.5 31.9 127.5 127.5 231.1 ...
?.. ..$ values: num [1:8060] 127.5 31.9 127.5 127.5 231.1 ...
?.. and so on

--
Michael Sumner
Institute for Marine and Antarctic Studies, University of Tasmania
Hobart, Australia
e-mail: mdsumner at gmail.com

I was a bit hasty. The SpatialGridDataFrame contains 325 separate grids each with 155 cols and 52 rows. E.g., if it were an array I'd think it would have dimensions of 52, 155, 325 and I'd want to do something like: monthly.sp[,,-1]. When I'm done I want the object to have 324 variables with 8060 obs and keep the cells.dim at 155 by 52.

-----Original Message-----
From: Matthew Landis [mailto:landis at isciences.com]
Sent: Tuesday, August 10, 2010 12:56 PM
To: r-sig-geo at stat.math.ethz.ch; Andy Bunn
Subject: Re: [R-sig-Geo] drop layer/band from SpatialGridDataFrame

  Andy - how about these two options

monthly.sp at data <- monthly.sp at data[-1,]

or (cheating with the help of raster package)

monthly.stack <- as(monthly.sp, 'RasterStack')
monthly.stack <- dropLayer(monthly.stack, 1)
monthly.sp <- as(monthly.stack, 'SpatialGridDataFrame')

Apologies if these are nonsense - I don't have time to actually test
these out on a toy example at the moment.

Matt

On 8/10/2010 3:02 PM, Andy Bunn wrote:

I was a bit hasty. The SpatialGridDataFrame contains 325 separate

grids each with 155 cols and 52 rows. E.g., if it were an array I'd
think it would have dimensions of 52, 155, 325 and I'd want to do
something like: monthly.sp[,,-1]. When I'm done I want the object to
have 324 variables with 8060 obs and keep the cells.dim at 155 by 52.

--
~~~~~~~~~~~~~~~~~~~~~~~~~~
Matthew Landis, Ph.D.
Research Scientist
ISciences, LLC
61 Main St. Suite 200
Burlington VT 05401
802.864.2999
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