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I am extracting raster data using GDAL from a map that has different shades of red depending on the temperature. When I run the code within QGIS only the beginning and end of the code shows up. This is why I want to export the data into Excel, but QGIS keeps crashing when I run that part of the code. I have tried exporting the data into .csv and .txt formats but I get a Permission Denied error.

from osgeo import gdal

import pandas as pd


import openpyxl


layers=QgsProject.instance ().mapLayersByName ('1970-2000, 2.5, feb')


layer=layers [0]


ds=gdal.Open (layer.dataProvider().dataSourceUri ())


dem_arr=ds.GetRasterBand (1).ReadAsArray ()


print (dem_arr)


df=pd.DataFrame (dem_arr)


df.to_excel ("colorfirst.xlsx")
PolyGeo
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avinator
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    Why not export it using pyqgis? I recommend this answer: https://gis.stackexchange.com/a/309117/120426 – Leo Cardona Aug 13 '20 at 21:16
  • Thank you for the response. For QgsVectorFileWriter.writeAsVectorFormat(layer, path, "utf-8", layer.crs(), 'xlsx') would I substitute the layer name as a string in place for the layer parameter. I tried this and it does not seem to work. Sorry, I am new to QGIS. – avinator Aug 13 '20 at 21:29
  • In fact, I get the error: overload 3: argument 1 has unexpected type 'QgsRasterLayer' – avinator Aug 13 '20 at 21:48
  • Sorry, the QgsVectorFileWriter class is used for vectoreal files. Would you like to export your data to xyz format (https://gdal.org/drivers/raster/xyz.html) and then to excel? – Leo Cardona Aug 13 '20 at 22:24
  • Yes, that is what I would like to do. Thanks. – avinator Aug 13 '20 at 22:27

1 Answers1

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You can export your raster file to xyz file, which you can open from Excel. The conversion is done using GDAL alg.

import processing

layers = QgsProject.instance().mapLayersByName('1970-2000, 2.5, feb')
layer = layers[0]
output = '/home/grand/Desktop/QGISOutputs/colorfirst.xyz'


Export raster layer to xyz file


result = processing.run("gdal:translate", 
        {'INPUT': layer,
        'TARGET_CRS':None,
        'NODATA':None,  # Assign a specified nodata value to output bands.
        'COPY_SUBDATASETS':False,
        'OPTIONS':'',
        'EXTRA':'',
        'DATA_TYPE':0,
        'OUTPUT': output})


print('Your file was created: {}'.format(result['OUTPUT']))

Note: Verify that the output directory exists before running the script otherwise the output file will not be created

You can also use gdal directly to do the conversion:

gdal_translate -of XYZ /home/ai/Desktop/input.tif /home/ai/Desktop/output.xyz
Leo Cardona
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