Plotting lines with equidistant points for identification
On 04/19/2011 06:05 PM, Timo Schneider wrote:
Dear R Gurus, I would like to make a line-plot of a large data-set (>200 data-points) for a document which will be printed in black and white. The plot will contain 5 different lines. So i need a way to differentiate between the lines. Since color is not an option i tried different line styles with all sorts of "line-gap" or "dot dot dot" patterns. Since my plots are rather small it is hard to get lines that look contiguous enough while still being identifiable through their line style. What I would like to have are lines that have symbols on top of them, similar to what i get with plot(x,y,type='o'). The problem is that i have to many data-points for that method, the symbols will just "melt together", as in plot(seq(1,500), seq(1,500), type='o') - just one big line. What i want is to have a configurable number of symbols spread equidistantly over the whole graph, regardless of the number or position of data-points. Does anyone have an idea how to achieve this?
Hi Timo, I don't have time to program this at the moment, but the method isn't too hard, assuming that your line is defined by a series of x and y coordinates. Define a function, e.g. equiPoints Pass the x and y coordinate vectors and the distance between symbols Start at the leftmost end of the line, recording the x/y coordinates Calculate the length of successive segments until the cumulative length is >= the desired distance Interpolate the x and y coordinates of the last segment to get the next position for a symbol Add these x and y coordinates to the x and y coordinate vectors Repeat until you reach the end of the line Use the symbols function to plot the symbols at the coordinates you have calculated Jim