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I have a CSV of biweekly temperature values for the year 2011, at a 1000-m scale in part of the state of Iowa. The CSV contains ~95000 rows of temperature data, with the first 2 columns as the x and y points and the subsequent 27 columns are the 14-day intervals. I am trying to convert the CSV into a raster stack at 30-m resolution using interpolation, where each layer of the stack is a biweekly period (27 layers). The code I am using to convert from a CSV to raster stack also uses a reference raster, which is a raster layer of the correct extent and 30-m resolution.

This code has worked for me before for smaller CSV files.

preview of what the CSV looks like (the temperature values purposefully do not make sense here)

pts <- read.csv("bimonthly_1000m_temp.csv")

ref = raster("~/reference_raster.tif")
u=crs(ref)

coordinates(pts)=~y+x 
proj4string(pts)=CRS("+init=epsg:4326") # set it to lat-long
pts = spTransform(pts,crs(u))
gridded(pts) = TRUE
r = stack(pts)
projection(r) = crs(u)
r_crop <- crop(r,ref)
extent(r_crop)=extent(ref)
r_crop_resam = resample(r_crop, ref, method='bilinear', filename = "~/interpolated_raster.tif")

But, I get an error at gridded(pts) = TRUE:

suggested tolerance minimum: 0.111429 
Error in points2grid(points, tolerance, round) : 
  dimension 1 : coordinate intervals are not constant

Any suggestions? This answer here is in the vein of what I am looking for, though I am trying to interpolate and creating a raster stack.

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    if the points fall on a grid you should create the raster before transforming them (what is the crs(u)? Try rasterFromXYZ(pts) directly after read.csv (before and instead ofusing the sp coordinates/gridded stuff) – mdsumner Jul 8 '20 at 23:06
  • Does "at a 1000-m scale" mean your points in the CSV are roughly 1000m apart? And you want to sample that up to a 30m resolution? – Spacedman Jul 9 '20 at 7:34
  • Thanks @mdsumner. I tried rasterFromXYZ() but got Error in rasterFromXYZ(dt) : x cell sizes are not regular. So I think the problem must be with my pts (my CSV file itself), it seems like they do not fall on a grid. – rachell Jul 10 '20 at 17:47
  • @Spacedman yes, exactly that. – rachell Jul 10 '20 at 17:48
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    "if the points fall on a grid" - try plotting them, it's often fairly clear - use 'pch = "."' so it's fast to plot many points – mdsumner Jul 14 '20 at 1:11

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