Changes between Version 39 and Version 40 of WKTRaster/SpecificationWorking03

Timestamp:

Mar 14, 2011, 11:56:15 AM (13 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationWorking03

@@ -203 +203 @@
 An alternative syntax would involve another function name (e.g. ST_MapAlgebraNgb) and a way to define a neighbour rectangular region around the computed pixel (e.g.: "2,2" meaning a rectangle encompassing the two neighbour pixels in each direction) and a function to call with this matrix of pixel values. A complete example might look like:
 
-SELECT ST_MapAlgebraNgb(rast, "ST_Avg", 2, 2, "ignore") 
+SELECT ST_MapAlgebraNgb(rast, "ST_Mean", 2, 2, "ignore") 
 
 So this would mean "for each pixel, compute the average of all the 1 + 8 + 16 = 25 pixels surrounding the current pixel and "ignore" pixels with nodata values."
 
-The "ST_Avg" summarizing function should accept three parameters: an array of float8 values, a X and a Y dimension, and optionnally a "what to do with nodata values". The possible value for this last parameter could be:
+The "ST_Mean" summarizing function should accept three parameters: an array of float8 values, a X and a Y dimension, and optionnally a "what to do with nodata values". The possible value for this last parameter could be:
 
  * "NULL": If any value is a nodata value, return NULL.
  * "ignore": Ignore any nodata value so that if 4 pixels on 25 are nodata values, do the computation with the 21 remaining.
+ * "value": Replace any nodata value with the value of the pixel being computed.
  * a value: Replace any nodata value with this value and compute.
 
 Any remaining parameters to ST_MapAlgebraNgb could be passed to the summarizing functions for its own need (e.g. "round" to specify that only the pixel forming a circle should be used in the computing).
 
-A number of predefined summarizing function could be delivered: ST_Average, ST_Majority, ST_Slope, ST_Aspect, 
+A number of predefined summarizing function could be delivered: ST_Sum, ST_Distinct, ST_Mean, ST_STD, ST_Max, ST_Min, ST_Range, ST_Median, ST_Majority, ST_Minority, ST_Slope, ST_Aspect, 
 
 Users could write their own map algebra summarizing functions.