move clear rect up to scatterplot, since drawscatterplot is now per cell

src/components/scatterplot/scatterplot.js

@@ -74,6 +74,8 @@ class Scatterplot extends React.Component {
       this.state.xScale &&
       this.state.yScale
     ) {
+      /* clear canvas */
+      this.state.ctx.clearRect(0, 0, width, height);
       drawScatterplotCanvas(
         this.state.ctx,
         this.state.xScale,