                     return
             }
             
-            let authorsInRepoSet = Set(json.values.flatMap({ $0.keys }))
-            let authorsInRepo = Array(authorsInRepoSet).sort()
+            let authorsInRepo = Array(Set(json.values.flatMap({ $0.keys }))).sort()
             
             // draw repo name
             c.drawText(repo, origin: P(LEFT_MARGIN_WIDTH, c.height() - self.TOP_MARGIN_HEIGTH - (currentRow) * ROW_HEIGHT - 18))

        guard let fromDate = self.dateFormatter.dateFromString(fromDay) else { assertionFailure(); return [] }
        guard let toDate = self.dateFormatter.dateFromString(toDay) else { assertionFailure(); return [] }
        
        var offset = 0
        
        calendar.enumerateDatesStartingAfterDate(fromDate, matchingComponents: matchingComponents, options: .MatchStrictly) { (date: NSDate?, exactMatch: Bool, stop: UnsafeMutablePointer<ObjCBool>) -> Void in
            

            
            // draw cells
            
            // for each author in the repo
            for (i, author) in authorsInRepo.enumerate() {
                
                // for each day of the timeframe
                for (day, _, offset) in dayTuples {
                    
                    // set default color
                    var fillColor = NSColor.clearColor()
