trying to change size of heatmap layer

leaflet.heat.js

/*(c) 2014, Vladimir Agafonkin
 Leaflet.heat, a tiny and fast heatmap plugin for Leaflet.
 https://github.com/Leaflet/Leaflet.heat
*/
L.HeatLayer = L.Class.extend({

    // options: {
    // maxZoom: 18,
    // radius: 25,
    // blur: 15,
    // max: 1.0
    // },

    initialize: function (latlngs, options) {
        this._latlngs = latlngs;
        L.setOptions(this, options);
    },

    setLatLngs: function (latlngs) {
        this._latlngs = latlngs;
        return this.redraw();
    },

    addLatLng: function (latlng) {
        this._latlngs.push(latlng);
        return this.redraw();
    },

    setOptions: function (options) {
        L.setOptions(this, options);
        if (this._heat) {
            this._updateOptions();
        }
        return this.redraw();
    },

    redraw: function () {
        if (this._heat && !this._frame && !this._map._animating) {
            this._frame = L.Util.requestAnimFrame(this._redraw, this);
        }
        return this;
    },

    onAdd: function (map) {
        this._map = map;

        if (!this._canvas) {
            this._initCanvas();
        }

        map._panes.overlayPane.appendChild(this._canvas);

        map.on('moveend', this._reset, this);

        if (map.options.zoomAnimation && L.Browser.any3d) {
            map.on('zoomanim', this._animateZoom, this);
        }

        this._reset();
    },

    onRemove: function (map) {
        map.getPanes().overlayPane.removeChild(this._canvas);

        map.off('moveend', this._reset, this);

        if (map.options.zoomAnimation) {
            map.off('zoomanim', this._animateZoom, this);
        }
    },

    addTo: function (map) {
        map.addLayer(this);
        return this;
    },

    _initCanvas: function () {
        var canvas = this._canvas = L.DomUtil.create('canvas', 'leaflet-heatmap-layer leaflet-layer');

        var size = this._map.getSize();
        canvas.width = size.x * 3;
        canvas.height = size.y * 3;

        var animated = this._map.options.zoomAnimation && L.Browser.any3d;
        L.DomUtil.addClass(canvas, 'leaflet-zoom-' + (animated ? 'animated' : 'hide'));

        this._heat = simpleheat(canvas);
        this._updateOptions();
    },

    _updateOptions: function () {
        this._heat.radius(this.options.radius || this._heat.defaultRadius, this.options.blur);

        if (this.options.gradient) {
            this._heat.gradient(this.options.gradient);
        }
        if (this.options.max) {
            this._heat.max(this.options.max);
        }
    },

    _reset: function () {
    	var size = this._map.getSize();

        var topLeft = this._map.containerPointToLayerPoint([0, 0]);
        L.DomUtil.setPosition(this._canvas, topLeft);

        if (this._heat._width !== size.x * 3) {
            this._canvas.width = this._heat._width = size.x * 3;
        }
        if (this._heat._height !== size.y * 3) {
            this._canvas.height = this._heat._height = size.y * 3;
        }

        this._redraw();
    },

    _redraw: function () {
        var data = [],
            r = this._heat._r,
            size = this._map.getSize(),
            bounds = new L.LatLngBounds(
                this._map.containerPointToLatLng(L.point([-size.x-r, -size.y-r])),
                this._map.containerPointToLatLng(size.add([size.x+r, size.y+r]))),
            maxZoom = this.options.maxZoom === undefined ? this._map.getMaxZoom() : this.options.maxZoom,
            v = 1 / Math.pow(2, Math.max(0, Math.min(maxZoom - this._map.getZoom(), 12))),
            cellSize = r / 2,
            grid = [],
            panePos = this._map._getMapPanePos(),
            offsetX = panePos.x % cellSize,
            offsetY = panePos.y % cellSize,
            i, len, p, cell, x, y, j, len2, k;

        // console.time('process');
        for (i = 0, len = this._latlngs.length; i < len; i++) {
            if (bounds.contains(this._latlngs[i])) {
                p = this._map.latLngToContainerPoint(this._latlngs[i]);
                x = Math.floor((p.x - offsetX) / cellSize) + 2;
                y = Math.floor((p.y - offsetY) / cellSize) + 2;

                k = (this._latlngs[i].alt || 1) * v;

                grid[y] = grid[y] || [];
                cell = grid[y][x];

                if (!cell) {
                    grid[y][x] = [p.x, p.y, k];

                } else {
                    cell[0] = (cell[0] * cell[2] + p.x * k) / (cell[2] + k); // x
                    cell[1] = (cell[1] * cell[2] + p.y * k) / (cell[2] + k); // y
                    cell[2] += k; // cumulated intensity value
                }
            }
        }

        for (i = 0, len = grid.length; i < len; i++) {
            if (grid[i]) {
                for (j = 0, len2 = grid[i].length; j < len2; j++) {
                    cell = grid[i][j];
                    if (cell) {
                        data.push([
                            Math.round(cell[0]),
                            Math.round(cell[1]),
                            Math.min(cell[2], 1)
                        ]);
                    }
                }
            }
        }
        // console.timeEnd('process');

        // console.time('draw ' + data.length);
        this._heat.data(data).draw();
        // console.timeEnd('draw ' + data.length);

        this._frame = null;
    },

    _animateZoom: function (e) {
        var scale = this._map.getZoomScale(e.zoom),
            offset = this._map._getCenterOffset(e.center)._multiplyBy(-scale).subtract(this._map._getMapPanePos());

        this._canvas.style[L.DomUtil.TRANSFORM] = L.DomUtil.getTranslateString(offset) + ' scale(' + scale + ')';
        // L.DomUtil.setTransform(this._canvas, offset, scale);
    }
});

L.heatLayer = function (latlngs, options) {
    return new L.HeatLayer(latlngs, options);
};