I all I am trying to create a matrix for a network diagram: # 1. The following produces two dataframes. The table "place" is a dataframe of all places made from "tra" a tracing table that has the source place and destination place. The table "details" is a dataframe of all source and destination properties. src=rep(c(1:3),each=5) des=c(16:30) rsk=rep(3,5) tra=data.frame(src,des,rsk) ips=data.frame(c(1:40),c(41:80),c(81:120)) colnames(ips)=c("placeid","x","y") place=c(tra$src,tra$des) place=data.frame(unique(place)) colnames(place)="placeid" place details=merge(ips, place, by.x = "placeid", by.y = "placeid")[1:3] details # 2. The goal is to produce a matrix with source properties as rows and destination properties as columns and a risk value (from the "details" table) placed in the matrix where a trace has occurred. All other values would be zero. trace.sna = matrix(rep(0, times = length(details[,1])^2), nrow =length(details[,1])) trace.sna for(i in 1:length(tra[,1])){ src = tra[i,1] des = tra[i,2] trace.sna[src, des]=tra[i,3]} I get the error message: Error in trace.sna[src, des] = tra[i, 3] : subscript out of bounds There is something wrong with the highlighted code. I know that there must be some descrepancy in the numbers of values I am using but don't know why or how to fix it. Thanks for your help in advance. Kind regards andy Andrew McFadden MVS BVSc Incursion Investigator Investigation & Diagnostic Centres - Wallaceville Biosecurity New Zealand Ministry of Agriculture and Forestry ######################################################################## This email message and any attachment(s) is intended solely for the addressee(s) named above. The information it contains is confidential and may be legally privileged. Unauthorised use of the message, or the information it contains, may be unlawful. If you have received this message by mistake please call the sender immediately on 64 4 8940100 or notify us by return email and erase the original message and attachments. Thank you. The Ministry of Agriculture and Forestry accepts no responsibility for changes made to this email or to any attachments after transmission from the office. ######################################################################## [[alternative HTML version deleted]]