refactor: reuse variance in chi/stdev implementation

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---

Author: Om-A-osc

lib/node_modules/@stdlib/stats/base/dists/chi/stdev/lib/main.js

@@ -20,9 +20,8 @@
 
 // MODULES //
 
-var isnan = require( '@stdlib/math/base/assert/is-nan' );
-var mean = require( '@stdlib/stats/base/dists/chi/mean' );
 var sqrt = require( '@stdlib/math/base/special/sqrt' );
+var variance = require( '@stdlib/stats/base/dists/chi/variance' );
 
 
 // MAIN //
@@ -50,12 +49,7 @@ var sqrt = require( '@stdlib/math/base/special/sqrt' );
 * // returns NaN
 */
 function stdev( k ) {
-	var mu;
-	if ( isnan( k ) || k < 0.0 ) {
-		return NaN;
-	}
-	mu = mean( k );
-	return sqrt( k - ( mu*mu ) );
+	return sqrt( variance( k ) );
 }
 
 

lib/node_modules/@stdlib/stats/base/dists/chi/stdev/manifest.json

@@ -39,9 +39,8 @@
       "libpath": [],
       "dependencies": [
         "@stdlib/math/base/napi/unary",
-        "@stdlib/math/base/assert/is-nan",
         "@stdlib/math/base/special/sqrt",
-        "@stdlib/stats/base/dists/chi/mean"
+        "@stdlib/stats/base/dists/chi/variance"
       ]
     },
     {
@@ -56,9 +55,8 @@
       "libraries": [],
       "libpath": [],
       "dependencies": [
-        "@stdlib/math/base/assert/is-nan",
         "@stdlib/math/base/special/sqrt",
-        "@stdlib/stats/base/dists/chi/mean"
+        "@stdlib/stats/base/dists/chi/variance"
       ]
     },
     {
@@ -73,9 +71,8 @@
       "libraries": [],
       "libpath": [],
       "dependencies": [
-        "@stdlib/math/base/assert/is-nan",
         "@stdlib/math/base/special/sqrt",
-        "@stdlib/stats/base/dists/chi/mean"
+        "@stdlib/stats/base/dists/chi/variance"
       ]
     }
   ]

lib/node_modules/@stdlib/stats/base/dists/chi/stdev/src/main.c

@@ -16,9 +16,8 @@
 * limitations under the License.
 */
 
-#include "stdlib/stats/base/dists/chi/mean.h"
-#include "stdlib/math/base/assert/is_nan.h"
 #include "stdlib/math/base/special/sqrt.h"
+#include "stdlib/stats/base/dists/chi/variance.h"
 
 /**
 * Returns the standard deviation of a chi distribution.
@@ -31,10 +30,5 @@
 * // returns ~0.697
 */
 double stdlib_base_dists_chi_stdev( const double k ) {
-	double mu;
-	if ( stdlib_base_is_nan( k ) || k < 0.0 ) {
-		return 0.0/0.0; // NaN
-	}
-	mu = stdlib_base_dists_chi_mean( k );
-	return stdlib_base_sqrt( k - ( mu*mu ) );
+	return stdlib_base_sqrt( stdlib_base_dists_chi_variance( k ) );
 }