Since x is temporal here (dates), you should probably use a rectY mark instead of barY. And you can use the binX transform to aggregate the data. For example: Plot.rectY(FailHeb.sheet("Region").slice(2), Plot.binX({y: "sum"}, {x: "C", y: "E"})) I also added the slice(2) since the first two rows in your spreadsheet don’t contain data.