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71 lines
1.9 KiB
ReStructuredText
71 lines
1.9 KiB
ReStructuredText
GRID CALCULATOR
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===============
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Description
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-----------
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The raster calculator allows the computation of algebraic expressions with raster layers, obtaining derived information in the form of new layers of geographical data
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The following operators and functions are available:
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- The following operators are available for the formula definition:
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- + Addition
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- - Subtraction
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- * Multiplication
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- / Division
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- ^ power
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- abs(x) - absolute value
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- sqrt(x) - square root
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- ln(x) - natural logarithm
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- log(x) - base 10 logarithm
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- exp(x) - exponential
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- sin(x) - sine
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- cos(x) - cosine
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- tan(x) - tangent
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- asin(x) - arcsine
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- acos(x) - arccosine
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- atan(x) - arctangent
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- atan2(x, y) - arctangent of x/y
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- gt(x, y) - if x>y the result is 1.0, else 0.0
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- lt(x, y) - if x<y the result is 1.0, else 0.0
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- eq(x, y) - if x=y the result is 1.0, else 0.0
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- mod(x, y) - returns the floating point remainder of x/y
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- ifelse(c, x, y) - if c=1 the result is x, else y
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- int(x) - integer part of floating point value x
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- pi() - returns the value of Pi
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If when calculating the value of a given cell, a no-data value appears in any of the layers used in the formula, the resulting value will always be a no-data value.
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Parameters
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----------
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- ``Grids[MultipleInput]``: The grids to use. They can be refered in the formula using letters (``a, b, c...``). The order for this naming is the same order as they appear in the selection window.
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- ``Formula[String]``: The formula to use, which can use any of the expressions listeed above.
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Outputs
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-------
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- ``Result[Raster]``: The resulting layer.
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Example
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-------
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You can for instance use the Grid Calculator module to flag 0 cells with -1:
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``ifelse(eq(a,0), (-1), b)``
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The formula reads like "if the cell is equal to zero, then write -1 else write the current value to the output grid".
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See also
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---------
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Console usage
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-------------
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::
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processing.runalg('saga:gridcalculator', grids, formula, use_nodata, result)
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