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  1. PO
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    <p>You can use <code>projectRaster</code> for this if you have a raster in one projection and resolution and you need output in a different particular resolution and projetion. </p> <p>The <code>from</code> argument is your high resolution raster and the <code>to</code> argument is your low res raster. Make sure you choose the correct method for aggregation (i.e. <code>bilinear</code> for continuous data and <code>ngb</code> (nearest neighbour) for categorical data.</p> <pre><code>require( raster ) # Projection info proj1 &lt;- CRS("+proj=laea +lon_0=20 +lat_0=5 +ellps=sphere +unit=km +to_meter=1e3") proj2 &lt;- CRS("+proj=longlat +datum=WGS84 +ellps=WGS84") # High res raster r1km &lt;- raster( nrows = 1515 , ncols = 2300 , xmn = -4000 , xmx = -1700 , ymn = -15 , ymx = 1500 , crs = proj1 ) # Low res raster r5km &lt;- raster( nrows = 303 , ncols = 460 , xmn = -20 , xmx = -5 , ymn = 4 , ymx = 15 , crs = proj2 ) # Set some values in high res raster pts &lt;- rasterToPoints(r1km) values( r1km ) &lt;- 0.01*pts[,1] + sin(0.02*pi*pts[,2]) # Reproject using the attributes of the low res raster for output out &lt;- projectRaster( from = r1km , to = r5km , method = "bilinear" ) # Plot - extent of second raster doesn't fully cover first so some data is missing par( mfrow = c(1,2) ) plot( r1km ) plot( out ) </code></pre> <p><img src="https://i.stack.imgur.com/U3YHt.png" alt="enter image description here"></p> <p>If your input and output data are the same except in resolution you can use aggregate...</p> <pre><code># If same extent and resolution require use aggregate r1 &lt;- raster(system.file("external/rlogo.grd", package="raster")) r5 &lt;- aggregate( r1 , fact = 5 , method = "bilinear" ) par( mfrow = c(1,2) ) plot( r1 ) plot( r5 ) </code></pre> <p><img src="https://i.stack.imgur.com/I0L7D.png" alt="enter image description here"></p>
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    1. POHow to resample a raster snapping to an existing grid?
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    1. USSimon O'Hanlon
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    1. COThanks but as my two files are in the same projection, the project does not work. About the aggregate, I cannot specify a file directly in order to snap to the grid, because I don't want to use a "fact" argument but a file?
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      1. USWraf
    2. CO@Wraf you should really provide a reproducible example showing what you have done then. I don't think I expend any more effort on this guessing at your requirements. Please read [**how to make a great reproducible example**](http://stackoverflow.com/q/5963269/1478381) and update your question accordingly!
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      1. USSimon O'Hanlon
    3. COThanks. Indeed, not easy to find an answer when not reproducible example is given. But the dataset used isquite big and making such example is not that easy.
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