v.univar: check if column exists

          extend example in the manual
          (merge r63889-90 from trunk)


git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@63891 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.univar/main.c

@@ -95,7 +95,7 @@ int main(int argc, char *argv[])
     G_add_keyword(_("attribute table"));
     G_add_keyword(_("geometry"));
     module->label =
-	_("Calculates univariate statistics for attribute.");
+	_("Calculates univariate statistics of vector map features.");
     module->description = _("Variance and standard "
 			    "deviation is calculated only for points if specified.");
 
@@ -347,17 +347,19 @@ void select_from_database(void)
 		      Fi->database, Fi->driver);
     db_set_error_handler_driver(Driver);
 
+    /* check if column exists */
+    ctype = db_column_Ctype(Driver, Fi->table, col_opt->answer);
+    if (ctype == -1)
+        G_fatal_error(_("Column <%s> not found in table <%s>"),
+                      col_opt->answer, Fi->table);
+    if (ctype != DB_C_TYPE_INT && ctype != DB_C_TYPE_DOUBLE)
+	G_fatal_error(_("Only numeric column type is supported"));
+    
     /* Note do not check if the column exists in the table because it may be an expression */
     db_CatValArray_init(&Cvarr);
-    nrec =
-	db_select_CatValArray(Driver, Fi->table, Fi->key, col_opt->answer,
-			      where_opt->answer, &Cvarr);
+    nrec = db_select_CatValArray(Driver, Fi->table, Fi->key, col_opt->answer,
+                                 where_opt->answer, &Cvarr);
     G_debug(2, "db_select_CatValArray() nrec = %d", nrec);
-
-    ctype = Cvarr.ctype;
-    if (ctype != DB_C_TYPE_INT && ctype != DB_C_TYPE_DOUBLE)
-	G_fatal_error(_("Column type not supported"));
-
     if (nrec < 0)
 	G_fatal_error(_("Unable to select data from table"));
 

vector/v.univar/v.univar.html

@@ -1,12 +1,12 @@
 <h2>DESCRIPTION</h2>
 
 <em>v.univar</em> calculates univariate statistics of vector map features.
-This includes the number of features counted, minimum and maximum values,
+This includes the number of features counted, minimum, maximum values,
 and range. 
 Variance and standard deviation is calculated only for points if
 <b>type=point</b> is defined.
 
-<p>Extended statistics adds median, 1st and 3rd quartiles, and 90th
+<p>Extended statistics (<b>-e</b>) adds median, 1st and 3rd quartiles, and 90th
 percentile to the output.
 
 <h2>NOTES</h2>
@@ -31,17 +31,83 @@ v.random output=samples npoints=100
 v.db.addtable map=samples columns="heights double precision"
 v.what.rast map=samples rast=elevation column=heights
 v.db.select map=samples
+</pre></div>
+
+Calculate height attribute statistics:
 
-# calculate height attribute statistics:
+<div class="code"><pre>
 v.univar -e samples column=heights type=point
+    
+number of features with non NULL attribute: 100
+number of missing attributes: 0
+number of NULL attributes: 0
+minimum: 57.2799
+maximum: 148.903
+range: 91.6235
+sum: 10825.6
+mean: 108.256
+mean of absolute values: 108.256
+population standard deviation: 20.2572
+population variance: 410.356
+population coefficient of variation: 0.187123
+sample standard deviation: 20.3593
+sample variance: 414.501
+kurtosis: -0.856767
+skewness: 0.162093
+1st quartile: 90.531
+median (even number of cells): 106.518
+3rd quartile: 126.274
+90th percentile: 135.023
+</pre></div>
+
+Compare to statistics of original raster map:
 
-# compare to statistics of original raster map:
+<div class="code"><pre>
 r.univar -e elevation
 
-# calculate distance between sampling points statistics:
-v.univar -d samples column=heights type=point
+total null and non-null cells: 2025000
+total null cells: 0
+
+Of the non-null cells:
+----------------------
+n: 2025000
+minimum: 55.5788
+maximum: 156.33
+range: 100.751
+mean: 110.375
+mean of absolute values: 110.375
+standard deviation: 20.3153
+variance: 412.712
+variation coefficient: 18.4057 %
+sum: 223510266.558102
+1st quartile: 94.79
+median (even number of cells): 108.88
+3rd quartile: 126.792
+90th percentile: 138.66
 </pre></div>
 
+Calculate distance between sampling points statistics:
+
+<div class="code"><pre>
+v.univar -d samples column=heights type=point
+
+number of primitives: 100
+number of non zero distances: 4851
+number of zero distances: 0
+minimum: 69.9038
+maximum: 18727.7
+range: 18657.8
+sum: 3.51907e+07
+mean: 7254.33
+mean of absolute values: 7254.33
+population standard deviation: 3468.53
+population variance: 1.20307e+07
+population coefficient of variation: 0.478132
+sample standard deviation: 3468.89
+sample variance: 1.20332e+07
+kurtosis: -0.605406
+skewness: 0.238688
+</pre></div>
 
 <h2>SEE ALSO</h2>