Hello, 

tripGrid() takes a trip object as input, but it returns a
SpatialGridDataFrame that is useable without the trip package itself. Use 
image(trg) or spplot(trg) to view it as an image. Plotting the grid
without any attribute information is the default behaviour for
SpatialGrids in the sp package. 

The tripGrid output is a single-attribute grid with the time spent stored 
in "z". 

The help pages for plotting SpatialGrids: 
library(sp)
?image.SpatialGridDataFrame
?spplot

Regards, Mike


==============Original message text===============
On Wed, 03 Jun 2009 0:48:04 +1000 Claire Tancell wrote:

I am trying to use the "trip" package to generate a map of time spent from 
a SpatialPointsDataFrame object using the tripGrid function and am having 
difficulty generating the final plot. The documentation seems to say that 
tripGrid generates a grid, carries out an interpolation, bins these 
interpolated points, and then counts the points allocated to each grid but 
it is not clear how to generate the final plot. Plotting the output of 
tripGrid just plots the grid itself. Does anyone have experience of using 
this package and advise me on how to generate the final time-spent plot?

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===========End of original message text===========



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Mike Sumner (Phd. Candidate)
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