I'm attempting to create my first function in R. The function should take in a data frame, x-series from data frame, y-series from data frame, and plot a scatter plot. Seems simple enough, but I run into trouble when I attempt to check for an optional boolean argument.
R Script
plotScatterChart <- function(data,x,y,scale=y,line=FALSE) { require(ggplot2) data$x <- as.numeric(x) data$y <- as.numeric(y) plot <- ggplot(data, aes(x, y)) + geom_point() + # aes(alpha=0.3,color=scale) #scale_color_gradient(high="red") if(line) { plot <- plot + geom_smooth(method="lm") } ggsave(file="plot.svg", plot=plot, height=10, width=10) return(plot) } plotScatterChart(data=iris,x=iris$Petal.Length,y=iris$Petal.Width,line=TRUE) Error
non-numeric argument to binary operator Extra
Other suggestions for improving this function are welcome.
23 Answers
The error is because of the trailing + after geom_point(). Remove that and it should work.
Christopher's answer is perfectly correct. Let me add that ggplot also seems to accept lists:
plot <- ggplot(data, aes(x, y)) + list( geom_point(), aes(alpha=0.3,color=scale), scale_color_gradient(high="red"), NULL ) Unfortunately, unlike Python where you can write [1, 2, 3, ], the construct list(1, 2, 3, ) produces an error in R. This is the reason for the final NULL, which is happily ignored by ggplot2.
Another possible workaround is to write
plot <- ggplot(data, aes(x, y)) + geom_point() + #aes(alpha=0.3,color=scale) + #scale_color_gradient(high="red") + list() The final list() is supposed to stay in place to cancel the effects of the last + sign; it is a no-op otherwise.
With version 2.0.0, ggplot2 has gained a new geometry, geom_blank() which draws nothing.
It can be used to avoid this type of errors when it is placed as last layer.
plot <- ggplot(data, aes(x, y)) + geom_point() + #aes(alpha=0.3,color=scale) + #scale_color_gradient(high="red") + geom_blank() Using geom_blank() in this way is similar to the workaround in @krlmlr's answer which uses list() as last layer.
