bugfix (float comparison)

- allow point increments to be arbitrary (for example 0.01)
- "sane" point increments as 0.25, 0.5, 1,... were not affected by this bug

statistics.Rnw

@@ -141,13 +141,18 @@ dset$value <- as.numeric(dset$value)
 total_points <- group_by(dset, Number) %>% summarize(s=sum(value))
 
 linscale <- data.frame(approx(int_points, int_grades, seq(0, maxpoints, by=dp)))
-scale <- data.frame(grade=floor(linscale$y*1/dg)*dg, s=linscale$x)
-grades <- data.frame(left_join(x=total_points, y=scale, by="s"))
+FUZZY <- 1e6
+linscale$jj <- as.integer(round(linscale$x*FUZZY))
+scale <- data.frame(grade=floor(linscale$y*1/dg)*dg, jj=linscale$jj)
+total_points$jj <- as.integer(round(total_points$s*FUZZY))
+grades <- data.frame(left_join(x=total_points, y=scale, by="jj"))
+grades <- grades[,c("Number", "s", "grade")]
 colnames(grades) <- c("legi", "points", "grade")
 grades$legi <- as.factor(grades$legi)
 ## plot grading scale (linear interpolation and projection to existing marks)
 scale_plot <- cbind(linscale, col=rep("linear interpolation", nrow(linscale)))
-colnames(scale_plot) <- c("s", "grade", "col")
+colnames(scale_plot) <- c("s", "grade", "jj", "col")
+scale$s <- scale$jj/FUZZY
 scale_plot <- rbind(scale_plot, cbind(scale, col=rep("rounded", nrow(linscale))))
 @