[processing] added short help for saga raster calculator

python/plugins/processing/algs/help/saga.yaml

@@ -0,0 +1,48 @@
+saga:rastercalculator: >
+  This algorithm allows to perform algebraic operations on raster layers
+
+  It requires a base layer, and a set of additional layers. The base layer is identified as "a" in the formula, while the additional layers are identified as "b, c, d...", using the order in which they appear in the multiple selection dialog.
+
+  The resulting layer has the extent and cellsize of the main layer.
+
+  The following operators and functions are available.
+
+  - Addition (+)
+
+  - Subtraction ( - )
+
+  - Multiplication (*)
+
+  - Division (/)
+
+  - Power (^)
+
+  - ln(x): returns natural logarithm of x.
+
+  - sin(x): returns the sine of x. x must be in radians
+
+  - cos(x): returns the cosine of x. x must be in radians
+
+  - cos(x): returns the tangente of x. x must be in radians
+
+  - asin(x): returns the arcsine of x, in radians
+
+  - acos(x): returns the arccosine of x, in radians
+
+  - atan(x): returns the arctangent of x, in radians
+
+  - atan2(x,y): returns the arctangent y/x, in radians
+
+  - abs(x): return the absolute value of x. abs(- 5)=5
+
+  - int(x): returns the integer part of x. int(5.4)=5
+
+  - mod(x,y): returns the modulus of x/y. mod(7,4)=3
+
+  - gt(x,y): true if x is greater than y
+
+  - lt(x,y): true if x is lower than y
+
+  - eq(x,y): true if x equals y. When using this function SAGA evaluates it in a per–cell basis. Therefore, eq(a,b) will not return 1 if grid a equals grid b. It will return 1 for those cells that have the same value in both grids, and zero otherwise.
+  
+  - ifelse(condition, x, y) returns x if condition evaluates to true (condition=1) or y if it evaluates to false