add CHIINV formula

cell/.unit-tests/FormulaTests.js

@@ -1065,6 +1065,15 @@ $( function () {
 		strictEqual( oParser.calculate().getValue().toFixed(7) - 0, 0.0500006, "CHIDIST(A2,A3)" );
 	} );
 
+	test( "Test: \"CHIINV\"", function () {
+		ws.getRange2( "A2" ).setValue( "0.050001" );
+		ws.getRange2( "A3" ).setValue( "10" );
+
+		oParser = new parserFormula( "CHIINV(A2,A3)", "A1", ws );
+		ok( oParser.parse(), "CHIINV(A2,A3)" );
+		strictEqual( oParser.calculate().getValue().toFixed(6) - 0, 18.306973, "CHIINV(A2,A3)" );
+	} );
+
 	test( "Test: \"BETA.INV\"", function () {
 		ws.getRange2( "A2" ).setValue( "0.685470581" );
 		ws.getRange2( "A3" ).setValue( "8" );

cell/model/FormulaObjects/statisticalFunctions.js

@@ -885,6 +885,18 @@
 		return res;
 	};
 
+	function CHIDISTFUNCTION(fp, fDF){
+		this.fp = fp;
+		this.fDF = fDF;
+	}
+	CHIDISTFUNCTION.prototype.GetValue = function(x){
+		var res;
+		var betaDistVal = getChiDist(x, this.fDF);
+		res = this.fp - betaDistVal;
+		return res;
+	};
+
+
 	/**
 	 * @constructor
 	 * @extends {AscCommonExcel.cBaseFunction}
@@ -1588,6 +1600,47 @@
 
 	cCHIINV.prototype = Object.create(cBaseFunction.prototype);
 	cCHIINV.prototype.constructor = cCHIINV;
+	cCHIINV.prototype.argumentsMin = 2;
+	cCHIINV.prototype.argumentsMax = 2;
+	cCHIINV.prototype.Calculate = function (arg) {
+		var oArguments = this._prepareArguments(arg, arguments[1], true);
+		var argClone = oArguments.args;
+
+		argClone[0] = argClone[0].tocNumber();
+		argClone[1] = argClone[1].tocNumber();
+
+		var argError;
+		if (argError = this._checkErrorArg(argClone)) {
+			return this.value = argError;
+		}
+
+		var calcTDist = function(argArray){
+			var fP = argArray[0];
+			var fDF = parseInt(argArray[1]);
+
+			if ( fDF < 1 || fP <= 0 || fP > 1){
+				return  new cError(cErrorType.not_numeric);
+			}
+
+			var aFunc = new CHIDISTFUNCTION(fP, fDF);
+			var oVal = iterateInverse(aFunc, fDF * 0.5, fDF);
+			var bConvError = oVal.bError;
+
+			if (bConvError){
+				return new cError(cErrorType.not_numeric);
+			}
+
+			var res = oVal.val;
+			return null !== res && !isNaN(res) ? new cNumber(res) : new cError(cErrorType.wrong_value_type);
+		};
+
+		return this.value = this._findArrayInNumberArguments(oArguments, calcTDist);
+	};
+	cCHIINV.prototype.getInfo = function () {
+		return {
+			name: this.name, args: "(probability, deg_freedom)"
+		};
+	};
 
 	/**
 	 * @constructor