Hey everyone, Im new to R and this forum so I apologize in advance for any
ambiguity in my question. What I want to do is create a spatiotemporal object
(class st) out of an esri shapefile with multiple features and csv file
containing data in long format (each row is one observation in space-time). So
what Ive done is imported the shapefile into r using
Library(rgdal)
# read in shape files
polygons.shp <- readOGR(polygon.shp", layer=polygon)
# rgdal returns the .prj file associated with the shapefile
print(proj4string(polygon.shp))
[1] "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"
# converted the csv file to a data.frame
long_format.df <- as.data.frame(long_format.csv)
# converted time variable to proper date format in R
long_format.df$Date <- as.Date(as.character(long_format.df$Date), format=
"%Y%m%d)
My long format table looks something like this: each location is associated
with an ID (that matches the polygon IDs in my shapefile) has a location name
and specific date and some variables. The variables fluctuate between
temporal and static. For example, X3 and X4 only change over space but not time
while X1 and X2 vary over space and time. The dates are the time at which the
space-time variables were collected (the last day of each month).
ID LocationName Date X1 X2 X3 X4...
1 California 2013-03-28 1 1 3 0
2 Washington 2013-03-28 0 1 9 9
3 Oregon 2013-03-28 1 3 0 8
1 California 2013-04-30 0 4 3 0
2 Washington 2013-04-30 5 9 9 9
3 Oregon 2013-04-30 1 0 0 8
1 California 2013-05-31 7 6 3 0
2 Washington 2013-05-31 0 0 9 9
3 Oregon 2013-05-31 1 5 0 8
When I try to use the stConstruct() I get this error:
stConstruct(long_format.df, long_format.df $ID, long_format.df $Date,
SpatialObj =polygon.shp, TimeObj = NULL)
Error in stConstruct(long_format.df, long_format.df $ID, long_format.df $Date,
SpatialObj =polygon.shp, TimeObj = NULL) :
unknown parameter combination
When I try to use the STFDF() I get this error:
STFDF(polygon, long_format.df$Date, long_format.df)
Error: nrow(object@data) == length(object@sp) * nrow(object@time) is not TRUE
I also created a separate xts time object in place of long_format.df$Date' and
tried that but it resulted in the same error.
Any help or advice would be much appreciated!!!
Best,
Cyrus
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