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I have a raster file (DEM) whose values range from 0 to 1565 meters (elevation). I want to extract a new raster file after classifying the values in four classes like this:

<= to 150 meters

150-600 meters

600-900 meters
>900 meters

after that I want to make statistical calculations.

How can I do this in QGIS?

I have installed the LecoS plugin and I probably don't have the NumPy, SciPy, Pip libraries installed, because it doesn't work.

• How can I see if I have these libraries?


• How do I install these libraries, if I don't have them?


• Is there an easiest way to extract a classified raster file?

I have Windows 7 Pro (64-bit) and QGIS 2.18.7

There is an easy way to reclassify a raster in QGIS using GRASS tool r.reclass. When you installed QGIS you probably installed GRASS as well. In the processing toolbox of QGIS go to GRASS/raster/r.reclass

Select the input raster layer, and then you can open a txt file containing reclassification rules. If you want 4 classes the file must contain the following:

1 thru 150 = 1
151 thru 600 = 2
601 thru 900 = 3
901 thru 1565 = 4

QGIS 3.2 has native, simple to use reclassification algorithms available through the processing toolbox.

You can check this out.
Go to QGIS Processing Toolbox, then follow the snaps. Hope this will help
Snap 1
Snap 2

It worked for me using the steps below....
Check min max values in first raster (dem),
Use Processing Toolbox > SAGA (2.3.2) > Reclassify values (simple)
Grid = dem (my first raster),
Replace Condition = [2] Low value <=grid valueLookup table = a fixed table with 4 rows created in Fixed table window,
Changed Grid = Save to temporary file,
Check on Open output file after running algorithm
Run (algorithm)
The Changed Grid raster appears on project.

After that arrange the style through properties and save as dem_reclass.tif
After that statistical analysis can be made through LecoS plugin (if it is installed)