Changes between Version 79 and Version 80 of WKTRaster/SpecificationWorking03

Timestamp:

05/16/11 11:50:40 (14 years ago)

Author:

dustymugs

Comment:

ST_Histogram

WKTRaster/SpecificationWorking03

@@ -820 +820 @@
 ST_ApproxMinMax('precip_2011', 'rast')
 }}}
+
+----
+
+'''ST_Histogram(raster, nband) -> set of records'''[[BR]]
+ST_Histogram and ST_ApproxHistogram provide methods to determine a raster's data distribution.
+
+The return of ST_Histogram and ST_ApproxHistogram is a set of records where each record is (min, max, count, proportion).
+
+ST_Histogram has the following variations.
+
+1. ST_Histogram(rast raster, nband int, hasnodata boolean, bins int, width double precision[], right boolean) -> set of records
+
+  returns set of records of four columns (min, max, count, proportion)
+
+  nband: index of band to process on
+
+  hasnodata: if FALSE, any pixel who's value is nodata is ignored.
+
+  bins: the number of categories/bins to have in the histogram. If NULL or value less than one, the number of categories will be auto-computed using Sturges' formula if the number of values >= 30 or Square-root choice if number of values < 30.
+
+    http://en.wikipedia.org/wiki/Histogram#Mathematical_definition
+
+  width: an array indicating the width of each category/bin. If the number of bins is greater than the number of widths, the widths are repeated. Example: 9 bins, widths are [a, b, c] will have the output be [a, b, c, a, b, c, a, b, c].
+
+  right: compute the histogram from the right rather than from the left (default). This changes the criteria for evaluating a value x from [a, b) to (a, b].
+
+{{{
+ST_Histogram(rast, 2, FALSE, NULL, NULL, FALSE)
+
+ST_Histogram(rast, 1, TRUE, 100, NULL, FALSE)
+
+ST_Histogram(rast, 2, FALSE, NULL, ARRAY[100, 50], FALSE)
+
+ST_Histogram(rast, 2, FALSE, 9, ARRAY[1000], TRUE)
+
+ST_Histogram(rast, 2, FALSE, 20, ARRAY[100, 200, 300], TRUE)
+}}}
+
+2. ST_Histogram(rast raster, nband int, hasnodata boolean, bins int, right boolean) -> set of records
+
+  parameter "width" is not specified thus resulting in all bins having the same widths
+
+{{{
+ST_Histogram(rast, 2, FALSE, 5, FALSE)
+}}}
+
+3. ST_Histogram(rast raster, nband int, hasnodata boolean, bins int) -> set of records
+
+  the parameter "right" is removed and assumed to be FALSE
+
+{{{
+ST_Histogram(rast, 2, FALSE, 5)
+}}}
+
+4. ST_Histogram(rast raster, nband int, hasnodata boolean) -> set of records
+
+  the parameter "bins" is removed and set to NULL.  The function will compute the number of bins to use
+
+5. ST_Histogram(rast raster, nband int) -> set of records
+
+  parameter "hasnodata" is removed and assumed to be FALSE
+
+6. ST_Histogram(rast raster) -> set of records
+
+  assumes that nband is 1.
+
+7. ST_Histogram(rast raster, nband int, bins int, width double precision[], right boolean) -> set of records
+
+  hasnodata is assumed to be FALSE
+
+8. ST_Histogram(rast raster, nband int, bins int, right boolean) -> set of records
+
+  all bins will have equal widths
+
+9. ST_Histogram(rast raster, nband int, bins int) -> set of records
+
+  right is assumed to be FALSE
+
+ST_ApproxHistogram should have the following variations.
+
+1. ST_ApproxHistogram(rast raster, nband int, hasnodata boolean, sample_percent double precision, bins int, width double precision[], right boolean) -> set of record
+
+    sample_percent: a value between 0 and 1 indicating the percentage of the raster band's pixels to consider when generating the histogram.
+
+{{{
+ST_Histogram(rast, 2, FALSE, 0.1, NULL, NULL, FALSE)
+
+ST_Histogram(rast, 1, TRUE, 1, 100, NULL, FALSE)
+
+ST_Histogram(rast, 2, FALSE, 0.2, NULL, ARRAY[100, 50], FALSE)
+
+ST_Histogram(rast, 2, FALSE, 0.25, 9, ARRAY[1000], TRUE)
+
+ST_Histogram(rast, 2, FALSE, 0.05, 20, ARRAY[100, 200, 300], TRUE)
+}}}
+
+2. ST_ApproxHistogram(rast raster, nband int, hasnodata boolean, sample_percent double precision, bins int, right boolean) -> set of records
+
+  parameter "width" is not specified thus resulting in all bins having the same widths
+
+3. ST_ApproxHistogram(rast raster, nband int, hasnodata boolean, sample_percent double precision, bins int) -> set of records
+
+  the parameter "right" is removed and assumed to be FALSE
+
+{{{
+ST_ApproxHistogram(rast, 2, FALSE, 5)
+}}}
+
+4. ST_ApproxHistogram(rast raster, nband int, hasnodata boolean, sample_percent double precision) -> set of records
+
+  the parameter "bins" is removed and set to NULL so that function can compute the number of bins to use
+
+5. ST_ApproxHistogram(rast raster, nband int, sample_percent double precision) -> set of records
+
+  parameter "hasnodata" is removed and assumed to be FALSE
+
+6. ST_ApproxHistogram(rast raster, nband int) -> set of records
+
+  assumes that sample_percent is 0.1
+
+7. ST_ApproxHistogram(rast raster, sample_percent double_precision) -> set of records
+
+  assumes that nband is 1
+
+8. ST_ApproxHistogram(rast raster) -> set of records
+
+  assumes that nband is 1 and sample_percent is 0.1
+
+9. ST_ApproxHistogram(rast raster, nband int, sample_percent double precision, bins int, width double precision[], right boolean) -> set of records
+
+  hasnodata is assumed to be FALSE
+
+10. ST_ApproxHistogram(rast raster, nband int, sample_percent double precision, bins int, right boolean) -> set of records
+
+  all bins will have equal widths
+
+11. ST_ApproxHistogram(rast raster, nband int, sample_percent double precision, bins int) -> set of records
+
+  right is assumed to be FALSE
 
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