Suppose I do a psychology experiment in which each of six subjects does several items in each of five fixed conditions, A, B, C, D, and E. The items are randomized separately for each subject, so I can ignore order. All I want to know is whether the five conditions differ. The data look like this. Each row is a subject, and each number is the score in the given condition. A B C D E 4 1 5 10 10 9 2 10 7 7 6 3 7 8 8 7 4 9 8 9 6 3 7 8 9 3 2 5 7 7 Question 1: This is the simplest possible repeated measures design. It should yield F(4,24)=16.033 for the effect of condition. (The example is from the Systat manual, slightly changed.) How do I show this with R? Question 2: I would like a graph in which each line is a subject, and the abscissa is labeled A B C D E. Thus, one line would connect the points 4 1 5 10 10. Another would connect 9 2 10 7 7, and so on. (Systat calls this a parallel plot, and I have come to find it very useful for a first look at data.) Can this be done in R? Jonathan Baron, Professor of Psychology, University of Pennsylvania Home page: http://www.sas.upenn.edu/~jbaron -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
Suppose I do a psychology experiment in which each of six subjects does several items in each of five fixed conditions, A, B, C, D, and E. The items are randomized separately for each subject, so I can ignore order. All I want to know is whether the five conditions differ. The data look like this. Each row is a subject, and each number is the score in the given condition. A B C D E 4 1 5 10 10 9 2 10 7 7 6 3 7 8 8 7 4 9 8 9 6 3 7 8 9 3 2 5 7 7 Question 1: This is the simplest possible repeated measures design. It should yield F(4,24)=16.033 for the effect of condition. (The example is from the Systat manual, slightly changed.) How do I show this with R? Question 2: I would like a graph in which each line is a subject, and the abscissa is labeled A B C D E. Thus, one line would connect the points 4 1 5 10 10. Another would connect 9 2 10 7 7, and so on. (Systat calls this a parallel plot, and I have come to find it very useful for a first look at data.) Can this be done in R? Jonathan Baron, Professor of Psychology, University of Pennsylvania Home page: http://www.sas.upenn.edu/~jbaron -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
Prof Brian D Ripley
2000-Mar-26 15:07 UTC
[R] very simple repeated measures, newbie questions
On Sun, 26 Mar 2000, Jonathan Baron wrote:> Suppose I do a psychology experiment in which each of six > subjects does several items in each of five fixed conditions, A, > B, C, D, and E. The items are randomized separately for each > subject, so I can ignore order. All I want to know is whether > the five conditions differ. The data look like this. Each row > is a subject, and each number is the score in the given > condition. > > A B C D E > 4 1 5 10 10 > 9 2 10 7 7 > 6 3 7 8 8 > 7 4 9 8 9 > 6 3 7 8 9 > 3 2 5 7 7 > > Question 1: This is the simplest possible repeated measures > design. It should yield F(4,24)=16.033 for the effect of > condition. (The example is from the Systat manual, slightly > changed.) How do I show this with R?There are some choices, but the simplest would be> score <- scan()1: 4 1 5 10 10 6: 9 2 10 7 7 11: 6 3 7 8 8 16: 7 4 9 8 9 21: 6 3 7 8 9 26: 3 2 5 7 7 31: Read 30 items> condition <- rep(LETTERS[1:5], len=30) > subject <- rep(1:6, rep(5,6)) > df <- data.frame(subject=factor(subject), condition, score) > summary(aov(score ~ subject + condition, data=df))Df Sum Sq Mean Sq F value Pr(>F) subject 5 20.567 4.113 1.9618 0.1287 condition 4 134.467 33.617 16.0334 4.969e-06 Residuals 20 41.933 2.097 Technically, I think you might want a random-effects analysis,> summary(aov(score ~ condition + Error(subject), data=df))but with such a simple design they are the same analysis.> Question 2: I would like a graph in which each line is a > subject, and the abscissa is labeled A B C D E. Thus, one line > would connect the points 4 1 5 10 10. Another would connect 9 2 > 10 7 7, and so on. (Systat calls this a parallel plot, and I > have come to find it very useful for a first look at data.) Can > this be done in R?Yes. (I guess you'd like to know how?) Here is one way: plot(c(1,5), range(score), type="n", xaxt="n", xlab="condition", ylab="score") axis(1, at=1:5, labels=LETTERS[1:5]) for(i in 1:6) lines(1:5, score[subject==i], type="o") Perhaps a simpler one is matplot(matrix(score, 5), type="l", xaxt="n") axis(1, at=1:5, labels=LETTERS[1:5]) -- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272860 (secr) Oxford OX1 3TG, UK Fax: +44 1865 272595 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._