Dear all, I'm looking for primary help at aggregating table() results and at writing a loop (if useful)
My dataset ( http://goo.gl/gEPKW ) is composed of 23k rows, each one representing a point in the space of which we know the land cover over 10 years (column y01 to y10). I need to analyse it with a temporal sliding window of 5 years (y01 to y05, y02 to y06 and so forth) For each period I'm looking for specific sequences (e.g., Maize, -noMaize, -noMaize, -noMaize, -noMaize) to calculate the "return time" of principal land covers: barley (2BC), colza (2Co), maize (2Ma), etc. I define the "return time" as the presence of a given land cover according to a given sequence. Hence, each return time could require the sum of different sequences (e.g., a return time of 5 years derives from the sum of [2Ma,no2Ma,no2Ma,no2Ma,no2Ma] + [no2Ma,no2Ma,no2Ma,no2Ma,2Ma]). I need to repeat the calculation for each land cover for each time window. In addition, I need to repeat the process over three datasets (the one I give is the first one, the second one is from year 12 to year 24, the third one from year 27 to year 31. So I have breaks in the monitoring of land cover that avoid me to create a continuous dataset). At the end I expect to aggregate the sum for each spatial entity (column WS) I've started writing the code for the first crop in the first 5yrs period (http://goo.gl/FhZNx) then copying and pasting it for each crop then for each time window... Moreover I do not know how to aggregate the results of table(). (NB sometimes I have a different number of WS per table because a given sequence could be absent in a given spatial entity... so I have the following warning msg: number of columns of result is not a multiple of vector length (arg 1)). Therefore, I'm "obliged" to copy&paste the table corresponding to each sequence.... FIRST QUEST. How to aggregate the results of table() when the number of columns is different? Or the other way around: Is there a way to have a table where each row reports the number of points per time return per WS? something like WS1 WS2 WS3 WS4 ... WS16 crop period 23 15 18 43 ... 52 Ma5 01 18 11 25 84 ... 105 Ma2 01 ... ... ... ... ... ... ... ... ... ... ... ... ... ... Co5 01 ... ... ... ... ... ... ... ... ... ... ... ... ... ... Ma5 02 ... ... ... ... ... ... ... ... In this table each row should represent a return time for a given land cover a given period (one of the 6 time window of 5 years)? SECOND QUEST. Could a loop (instead of a modular copy/paste code) improve the time/reliability of the calculation? If yes, could you please indicate me some entry-level references to write it? I am aware this are newbie's questions, but I have not be able to solve them using manuals and available sources. Thank you in advance for your help. Greetings, Dd PS R: version 2.14.2 (2012-02-29) OS: MS Windows XP Home 32-bit SP3 ***************************** Davide Rizzo post-doc researcher INRA UR055 SAD-ASTER website :: http://sites.google.com/site/ridavide/ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
