# [Qgis-user] Raster calculator script failing for multiple rasters

```Hi,

I'm trying to do raster calculations with big and multiple rasters. I am
new to python, but I managed to use the QgsRasterCalculator algorithm to do
the average of three rasters.```
```
The problem comes when I introduce a forth layer and try to do a more
complex equation:

#calculating c4s ( [c1-c2]*[c0-c3] )

#F1_30
A=processing.getObjectFromUri(path + "/F1_30c1.tif")
B=processing.getObjectFromUri(path + "/F1_c2.tif")
C=processing.getObjectFromUri(path + "/F1_30c0.tif")
D=processing.getObjectFromUri(path + "/F1_c3.tif")

entries=[]
rasA=QgsRasterCalculatorEntry()
rasA.ref='A@1'
rasA.raster=A
rasA.bandNumber=1
entries.append(rasA)

rasB=QgsRasterCalculatorEntry()
rasB.ref='B@1'
rasB.raster=B
rasB.bandNumber=1
entries.append(rasB)

rasC=QgsRasterCalculatorEntry()
rasC.ref='C@1'
rasC.raster=C
rasC.bandNumber=1
entries.append(rasC)

rasD=QgsRasterCalculatorEntry()
rasD.ref='D@1'
rasD.raster=D
rasD.bandNumber=1
entries.append(rasD)

F1_30c4=QgsRasterCalculator('(( A@1 - B@1 ) * ( C@1 - D@1 ))', path +
'/F1_30c4.tif', 'GTiff', base.extent(), base.width(), base.height(),
entries).processCalculation()

I think that the problem is recognising the formula. I have tried it on the
console doing several changes and it doesnt work.

Is it possible to do this operation with QgsRasterCalculator?? Or how can I
use the gdal_calc algorithm or the saga raster calculator??

Thanks all
```
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