text: /**
  * @license Apache-2.0
  *
  * Copyright (c) 2018 The Stdlib Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *    http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  
  'use strict';
  
  // MODULES //
  
  var incrmean = require( '@stdlib/stats/incr/mean' );
  var signum = require( '@stdlib/math/base/special/signum' );
  var kroneckerDelta = require( '@stdlib/math/base/special/kronecker-delta' );
  
  
  // MAIN //
  
  /**
  * Returns an accumulator function which incrementally computes the mean directional accuracy.
  *
  * @returns {Function} accumulator function
  *
  * @example
  * var accumulator = incrmda();
  *
  * var m = accumulator();
  * // returns null
  *
  * m = accumulator( 2.0, 3.0 );
  * // returns 1.0
  *
  * m = accumulator( -5.0, 4.0 );
  * // returns 0.5
  *
  * m = accumulator();
  * // returns 0.5
  */
  function incrmda() {
  	var mean;
  	var FLG;
  	var f0;
  	var a0;
  
  	mean = incrmean();
  	return accumulator;
  
  	/**
  	* If provided a value, the accumulator function returns an updated mean directional accuracy. If not provided a value, the accumulator function returns the current mean directional accuracy.
  	*
  	* @private
  	* @param {number} [f] - forecast value
  	* @param {number} [a] - actual value
  	* @returns {(number|null)} mean directional accuracy or null
  	*/
  	function accumulator( f, a ) {
  		var sf;
  		var sa;
  		if ( arguments.length === 0 ) {
  			return mean();
  		}
  		if ( FLG === void 0 ) {
  			FLG = true;
  			f0 = f;
  			a0 = a;
  		}
  		sf = signum( f-f0 );
  		sa = signum( a-a0 );
  		f0 = f;
  		a0 = a;
  		return mean( kroneckerDelta( sf, sa ) );
  	}
  }
  
  
  // EXPORTS //
  
  module.exports = incrmda;
  