el.innerHTML = '+';
    } else {
        e.style.display = 'block';
        el.innerHTML = '-';
    }
}

// TODO: scale the graph with the viewBox attribute.
function graphReduce(id) {
    var node = document.getElementById(id);
    if (node) {
    		node.width.baseVal.value *= 0.9;
    		node.height.baseVal.value *= 0.9;
    }
    return false;
}