Hey everyone, I’m 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 I’ve 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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