[R] Producing a matrix of values

From: Andrew McFadden <Andrew.McFadden_at_maf.govt.nz>
Date: Wed, 12 Nov 2008 10:29:55 +1300


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

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