Using the qplot command the line does not show

Question

This is a follow on from my last question relating to plotting timestamps in R. I am using the same XML file. The question has been answered and is working except for the following command:

qplot(timeStamp,Price,data=test.df,geom=c("point","line"),color="Measured", shape="Measured",linetype="Measured", scale_y_continuous(limits = c(10,26)))

The problem is that the line is not shown on the graph, but the points are. I have searched online but there does not seem to be a solution. Is there other options / additional commands I need to get the line to display?

Sorry if this seems such a simple question but I am a total beginner and have found the people on this site to be extremely helpful and this has been very much appreciated.

Answer 1

When the x-axis is a factor, you need to define the groups across which you want to draw the line. That is, if you want to draw a line for every unique group defined by A, you would pass group = A to qplot(). If the lines are going to be defined by a combination of A and B, you would pass group = A:B.

With this data, since there aren't any groups, defined in the data frame, pass group = 1 to qplot(). That should do the trick.

Answer 2

Your problem is probably that you haven't converted timeStamp to a time stamp - it's probably currently stored as a factor. Without seeing your data I can't tell you exactly what you need to do to fix it, but it's likely to involve strptime.