Add new SB function STATSTD (standard deviation)

samples/distro-examples/tests/all.bas

@@ -219,6 +219,7 @@ print "STATMEAN:" + STATMEAN (1,2,3,4,5,6,7,8,9)
 print "STATMEANDEV:" + STATMEANDEV (1,2,3,4,5,6,7,8,9)
 print "STATSPREADP:" + STATSPREADP (1,2,3,4,5,6,7,8,9)
 print "STATSPREADS:" + STATSPREADS (1,2,3,4,5,6,7,8,9)
+print "STATSTD:" + STATSTD (1,2,3,4,5,6,7,8,9)
 print "STR:" + STR (5)
 print "STRING:"; STRING(5, "Strings")
 print "SUM:" + SUM (1,2,3,4,5,6,7,8,9)

samples/distro-examples/tests/output/all.out

@@ -202,6 +202,7 @@ STATMEAN:5
 STATMEANDEV:2.22222222222222
 STATSPREADP:6.66666666666667
 STATSPREADS:7.5
+STATSTD:2.73861278752583
 STR:5
 STRING:StringsStringsStringsStringsStrings
 SUM:45

src/common/blib_func.c

@@ -2600,6 +2600,7 @@ void cmd_genfunc(long funcCode, var_t *r) {
     //
     //
   case kwSTATMEANDEV:
+  case kwSTATSTD:
   case kwSTATSPREADS:
   case kwSTATSPREADP:
     ready = 0;
@@ -2669,6 +2670,9 @@ void cmd_genfunc(long funcCode, var_t *r) {
       case kwSTATMEANDEV:
         r->v.n = statmeandev(dar, tcount);
         break;
+      case kwSTATSTD:
+        r->v.n = statstd(dar, tcount);
+        break;
       case kwSTATSPREADS:
         r->v.n = statspreads(dar, tcount);
         break;

src/common/blib_math.c

@@ -232,6 +232,31 @@ var_num_t statmeandev(var_num_t *e, int count) {
   return sum / count;
 }
 
+//
+// Standard deviation
+//
+var_num_t statstd(var_num_t *e, int count) {
+  var_num_t sum = 0.0;
+  var_num_t mean;
+  int i;
+
+  if (count == 0) {
+    return 0;
+  }
+
+  for (i = 0; i < count; i++) {
+    sum += e[i];
+  }
+  mean = sum / count;
+
+  sum = 0.0;
+  for (i = 0; i < count; i++) {
+    sum += pow(fabsl(e[i] - mean),2);
+  }
+
+  return sqrt(sum / (count - 1));
+}
+
 /*
  */
 var_num_t statspreads(var_num_t *e, int count) {

src/common/blib_math.h

@@ -66,19 +66,45 @@ var_num_t mat_determ(var_num_t *a, int n, double toler);
 
 /**
  * @ingroup math
- * todo: statmeandev
+ * 
+ * Mean absolute deviation around arithmetic mean
+ * 
+ * @param e array with numbers
+ * @param count number of elements of e
+ * @return the mean absolute deviation around arithmetic mean
  */
 var_num_t statmeandev(var_num_t *e, int count);
 
 /**
  * @ingroup math
- * todo: statspreads
+ * 
+ * Standard deviation
+ * 
+ * @param e array with numbers
+ * @param count number of elements of e
+ * @return the standard deviation
+ */
+var_num_t statstd(var_num_t *e, int count);
+
+/**
+ * @ingroup math
+ * 
+ * Unbiased sample variance
+ * 
+ * @param e array with numbers
+ * @param count number of elements of e
+ * @return Unbiased sample variance
  */
 var_num_t statspreads(var_num_t *e, int count);
 
 /**
  * @ingroup math
- * todo: statspreadp
+ * 
+ * Biased sample variance
+ * 
+ * @param e array with numbers
+ * @param count number of elements of e
+ * @return Biased sample variance
  */
 var_num_t statspreadp(var_num_t *e, int count);
 

src/common/eval.c

@@ -1175,6 +1175,7 @@ static inline void eval_callf(var_t *r) {
   case kwSUMSV:
   case kwSTATMEAN:
   case kwSTATMEANDEV:
+  case kwSTATSTD:
   case kwSTATSPREADS:
   case kwSTATSPREADP:
   case kwSEGCOS:

src/common/kw.h

@@ -348,6 +348,7 @@ enum func_keywords {
   kwSUM,
   kwSUMSV,
   kwSTATMEAN,
+  kwSTATSTD,
   kwSTATMEANDEV,
   kwSTATSPREADS,
   kwSTATSPREADP,

src/languages/keywords.en.c

@@ -288,6 +288,7 @@ struct func_keyword_s func_table[] = {
 { "SUM",                        kwSUM },
 { "SUMSQ",                      kwSUMSV },
 { "STATMEAN",                   kwSTATMEAN },
+{ "STATSTD",                    kwSTATSTD},
 { "STATMEANDEV",                kwSTATMEANDEV },
 { "STATSPREADS",                kwSTATSPREADS },
 { "STATSPREADP",                kwSTATSPREADP },