代打って効果あるの？

daida.js

var originalRatios = [
	.259, .337, .330, .267, .188, .274, .224, .227, .091
];

function calcHit(h, bases) {
	if(h > 2) {
		// homerun
		var s = 1 + (bases[0]?1:0) + (bases[1]?1:0) + (bases[2]?1:0);
		bases[0] = bases[1] = bases[2] = false;
		return s;
	}
	if(h == 2) {
		// two bases
		var s = 0;
		if(bases[2]) { bases[2] = false; s++; }
		if(bases[1]) { bases[1] = false; s++; }
		if(bases[0]) { bases[0] = false; bases[2] = true; }
		bases[1] = true;
		return s;
	}
	if(h == 1) {
		// hit
		var s = 0;
		if(bases[2]) { bases[2] = false; s++; }
		if(bases[1]) { bases[1] = false; s++; }
		if(bases[0]) { bases[0] = false; bases[1] = true; }
		bases[0] = true;
		return s;
	}
	return 0;
}

var daida = false;
var daidaInning = 7;
var daidaRatio = 0.3;
var daidaRatioAfter = 0.1;

var k = 1000000;
var sum = 0;
for(var i = 0; i < k; i++) {
	var ratios = [].concat(originalRatios);
	var currentDaida = daida;
	var inning = 1;
	var batter = 0;
	var score = 0;

	for(inning = 1; inning < 10; inning++) {
		//console.log("inning: " + inning);
		var bases = [false, false, false];
		var outs = 0;
		while(outs < 3) {
			var isDaida = false;
			if(currentDaida && inning >= daidaInning) {
				if(bases[2] || bases[1]) {
					isDaida = true;
					currentDaida = false;
					ratios[batter] = daidaRatio;
				}
			}
			var ratio = ratios[batter];
			var h = 0;
			do {
				var r = Math.random();
				var hit = false;
				if(r < ratio) {
					h++;
					hit = true;
				}
			} while(hit && h < 3);
			if(h == 0) {
				// out
				outs++;
			} else {
				// hit
				score += calcHit(h, bases);
			}
			if(isDaida) {
				if(batter == 8) {
					ratios[batter] = 0;
				} else {
					ratios[batter] = daidaRatioAfter;
				}
			}
			batter++;
			var s = (bases[0]?"o":"_") + (bases[1]?"o":"_") + (bases[2]?"o":"_");
			//console.log("batter " + batter + ": " + h + " " + s + " score: " + score);
			if(batter >= 9) { batter = 0; }
		}
	}
	//console.log("score: " + score);
	sum += score;
}
console.log("ave score:" + (sum / k));