add checks

TODO: provide meaningful error messages

statistics.Rnw

@@ -130,10 +130,12 @@ library(reshape)
 library(xtable)
 @
 
-<<prepare data, echo=FALSE, message=FALSE, warning=FALSE>>=
+<<prepare data, echo=FALSE, error=TRUE>>=
 ## read data
 dset <- read.csv('marks.csv', encoding='ISO-8859-1')
 dset <- dset[, !(names(dset) %in% c("Last.Name", "First.Name"))]
+stopifnot(length(dset)-1 == length(max_points_per_task))
+
 dset <- melt(dset, id=c("Number"))
 dset$value <- as.numeric(dset$value)
 total_points <- group_by(dset, Number) %>% summarize(s=sum(value))
@@ -149,7 +151,7 @@ colnames(scale_plot) <- c("s", "grade", "col")
 scale_plot <- rbind(scale_plot, cbind(scale, col=rep("rounded", nrow(linscale))))
 @
 
-<<store grades, echo=FALSE, warning=FALSE>>=
+<<store grades, echo=FALSE, warning=FALSE, error=TRUE>>=
 ## export (legi, grade) to csv
 write.csv(data.frame(Number=grades$legi, Grade=grades$grade, Points=grades$point),
           fileEncoding='ISO-8859-1',
@@ -160,7 +162,7 @@ write.csv(data.frame(Number=grades$legi, Grade=grades$grade, Points=grades$point
 
 \section*{Grades}
 \label{sec:grades}
-<<grades, echo=FALSE, warning=FALSE, fig.width=5, fig.height=5, out.width="0.49\\linewidth", fig.show='hold', fig.env="figure*", fig.subcap=c("Histogram", "CDF"), fig.pos='h!'>>=
+<<grades, echo=FALSE, warning=FALSE, error=TRUE, fig.width=5, fig.height=5, out.width="0.49\\linewidth", fig.show='hold', fig.env="figure*", fig.subcap=c("Histogram", "CDF"), fig.pos='h!'>>=
 ggplot(grades, aes(x=grade)) +
     geom_histogram(binwidth = 0.25, alpha=0.8) +
     scale_x_continuous(breaks=seq(1,6, by=1)) +
@@ -172,7 +174,7 @@ ggplot(grades, aes(x=grade)) +
 @ %def
 
 
-<<violing, echo=FALSE, fig.height=1, fig.width=3, fig.show='hold'>>=
+<<violing, echo=FALSE, error=TRUE, fig.height=1, fig.width=3, fig.show='hold'>>=
 ogrades <- cbind.data.frame(x=rep("grade", nrow(grades)), y=grades$grade)
 opoints <- cbind.data.frame(x=rep("points", nrow(grades)), y=grades$points)
 ggplot(ogrades, aes(x=x,y=y)) +