Having read the list posting guidelines I fear my first post is about to break the rules. Apologies in advance.
We have been asked to produce some graphs of relative performance of 3 groups of people in relation to the trend of their previous performance. I am neither a mathematician or a statistician, but wondered if R (which I have been using as a desktop calculator!) and some knowledge from this list may be able to help. We have a dataset something like this: group | previousavg | lastreading | finalreading ------------------------------------------------ 1 | 9.5 | 10 | 12 1 | 7 | 9 | 11 1 | 12 | 11 | 12 2 | 13 | 14 | 16 2 | 11 | 10 | 9 3 | 10 | 10 | 10.5 3 | 8.5 | 10 | 12 I need to produce some graphs typifying the change for each group between a _projected_ final reading and the final reading given. The time difference between previousavg and lastreading is 1/2 that between lastreading and finalreading. Where I have got to so far: I have read the result set (less than 200 rows) into a table 'results', attached it and then rather crudely constructed projected figures : results$projected = ((lastreading - previousavg) * 2) + lastreading then I can see the differentials between projected and finalreading: > result$projected - results$finalreading [1] -1.4 6.9 1.1 3.4 0.0 3.6 -3.8 0.1 -0.1 0.9 1.2 -3.4 -1.5 0.1 5.6 [16] -3.3 -1.9 0.9 -3.1 1.5 0.7 -1.6 -0.3 1.1 -0.1 -0.6 1.5 0.2 0.8 -1.0 [31] 0.8 -0.5 1.9 -4.0 -3.3 3.1 2.8 -0.6 1.2 2.0 -1.9 -1.6 -1.1 -3.9 NA ... Aims: - Summarise these by groups (I can't work out how to use tapply...) - Produce a sensible 'typification' of each group's change in relation to the projected figure. I assume this would use a statistical algorithm to exclude exceptions. - Plot the 3 'typifications' in sensible relation to each other, possibly with data points showing the source of these lines. My sincere apologies if this is completely off-topic for this list. I'm hoping to learn a little by understanding how certain functions are used (approaching this like a programmer rather than a statistician.) If I needed to learn more is the book "Introductory Statistics with R" a good place to start? Thanks Rory -- Rory Campbell-Lange <[EMAIL PROTECTED]> <www.campbell-lange.net> ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html