- ctx.beginPath();
- ctx.moveTo(px(data[0][0]), py(data[0][1]));
- for (i = 1; i < data.length; i++) {
- ctx.lineTo(px(data[i][0]), py(data[i - 1][1]));
- ctx.lineTo(px(data[i][0]), py(data[i][1]));
+ if (data.length) {
+ ctx.beginPath();
+ ctx.moveTo(px(data[0][0]), py(data[0][1]));
+ for (i = 1; i < data.length; i++) {
+ ctx.lineTo(px(data[i][0]), py(data[i - 1][1]));
+ ctx.lineTo(px(data[i][0]), py(data[i][1]));
+ }
+ ctx.strokeStyle = color;
+ ctx.stroke();