Re: [R] Plotting lines with equidistant points for identification

From: Jim Lemon <>
Date: Tue, 19 Apr 2011 18:31:45 +1000

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 mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Tue 19 Apr 2011 - 08:37:53 GMT

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