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I am trying to use the MODIStsp package to download MODIS data and convert it in a usable format (R table) to do statistical analysis. I downloaded the data, and loaded the virtual raster file in my R session : 

library(sp)
library(MODIStsp)

# loading virtual file 

virtual_file = "C:/Users/hp-8570w/Desktop/internship/MODIS_data/output/Surf_Temp_Daily_1Km_v6/Time_Series/RData/Terra/LST_Day_1km/MOD11A1.RData"
data = get(load(virtual_file))

And now I am trying to extract data at some specific points. For that, I have a set of points (latitudes and longitudes) stored in a dataframe with 2 columns. I create a SpatialPoints object : 

points = read.csv('points.csv',sep = " ")
projection = CRS('+proj=sinu +lon_0=0 +x_0=0 +y_0=0 +a=6371007.181+b=6371007.181 +units=m +no_defs')
spatial_points = SpatialPoints(points, proj4string = projection)

And I want to use the MODIStsp_extract() function : 

test_extract = MODIStsp_extract(data,spatial_points)

I get the following error message : 

Error in MODIStsp_extract(raster_ts, spatial_points) : 
no slot of name "data" for this object of class "SpatialPoints"

As the documentation shows (https://www.rdocumentation.org/packages/sp/versions/1.3-1/topics/SpatialPoints), SpatialPoints objects do not have a "data" field, but SpatialPointsDataFrame do. However, the data slot is intended for flat tables, with some data for every line, every line being a point. What I don't get is that I obviously don't have this data for every point : that's what I am trying to recover from the raster in the first place ! So obviously there is something I am doing wrong, but I can't see what.

If anoybody has any idea what I am doing wrong, that would be of great help !

a834311
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  • You can try transforming your SpatialPoints to a SpatialPointsDataFrame using something like `spatial_points = SpatialPointsDataFrame(spatial_points, data.frame(ID = 1:length(spatial_points)))`. This will add an "ID" column, which can also be useful later on to know which point is which. Alternatively, you can add an "ID" column directly in the points.csv file. – lbusett Aug 07 '19 at 14:33
  • I'll probably have to add some check on the function to avoid this kind of error, though. – lbusett Aug 07 '19 at 14:36

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