Greetings, I confess to being new to R, which I am exploring for some simulation modeling purposes. I am a long time programmer in PHP.
I am having some trouble getting over the "steep learning curve" with some very basic things which are probably just little "a-ha" things in R. I have hunted and hunted through the manual and cannot figure this one out, so I am appealing for help. I have the following program: results <- replicate(10000,0) for (year in 2000:2050) { print(year); for (i in 1:10000) { x=results[i]; if (x == 0) { prev = results[i-1]; next = results[i+1]; prob=0.1; if (i>=1) { if (prev==1) { prob=prob+0.4; } } if (i<10000) { if (next==1) { prob=prob+0.4; } } y=runif(1,0,1); if (y<prob) { x=1; } results[i]=x; } } } No matter how I try this (and I've tried a number of variations), I get an error similar to Error in next = results[i + 1] : invalid (NULL) left side of assignment I need to be able to loop through the results vector and compare the previous/next items in the list to the current one. Is that possible? What am I missing? Cordially, Justin Long ______________________________________________ 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.