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First, I want to clarify this is a very basic question. I'm new using R (and programming in general).

I have a data.frame with 3 columns:

block, average condition 1, average condition 2.

The blocks run from 1 to 9 and the average are response times averaged across subjects. What I want to do is to plot both averages, one for each condition, while having in the x axis the progression of blocks. Therefore, I would expect to have one line for each condition running above the x axis.

My question is what plot function should I use. I've tried with nearly everyone but what I thought would serve (simply plotting a vector with two columns as entry, against the block column) doesn't work, it gives the error:

 'x' and 'y' lengths differ

So I thought I should first plot only one condition and then somehow add the other line with a second command. I successfully plotted one condition as I wanted to:

plot(meanrts2[,3],meanrts2[,2],ylab="RT",xlab="block",type="l")

So here I'm choosing the 3rd and 2nd columns to do the plotting, but what I want is to have two columns running parallel, each one with different colors.

I tried abline, using the other columns I haven't plotted yet as an argument, but I get the "invalid a=, b= specification"

Any suggestions are very welcome. Any other information I missed you can always ask.

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points(meanrts2[,3],meanrts2[,1],ylab="RT",xlab="block",type="l")

or

lines(meanrts2[,3],meanrts2[,1],ylab="RT",xlab="block")

would suffice... I guess

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  • $\begingroup$ Thanks for your answer. Indeed the lines() function worked for me, though in a slightly different way. First I created my plot with column 1(y axis) and 3 (x axis): plot(meanrts2[,3],meanrts2[,1],ylab="RT",xlab="block",type="l") And then I just added the 2nd colum of my meanrts2 data.frame with this: lines(meanrts2[,2]) And I got the plot I wanted with the two lines stemming from the y axis and going across the x axis. $\endgroup$ – HernanLG May 9 '12 at 18:19
  • $\begingroup$ Seems like a good question and a good answer. I'm just confused because I've seen questions closed because they dealt only with how to program software and involved no statistical content. $\endgroup$ – rolando2 May 9 '12 at 21:44

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