Problems dealing with matrices

Hi,

Sorry for continuous bothering. Continuum of the previous problem...

I have the following matrices and vectors,

dcmat<-matrix(c(0.13,0.61,0.25,0.00,0.00,0.00,0.52,0.37,0.09,0.00,0.00,0.00, 
                0.58,0.30,0.11,0.00,0.00,0.00,0.46,0.22,0.00,0.00,0.00,0.00, 
                0.09),nrow=5,ncol=5) 

volini<-matrix(c(0,0,0,0,0),nrow=5,ncol=1)

volinp1<-c(0, 0.0004669094, 0.0027610861, 0.0086204692, 0.0200137754, 
0.0389069106 ,0.0670942588, 0.1060941424, 0.1570990708, 0.2209672605, 
0.2982420945, 0.3891882830, 0.4938361307, 0.6120278338, 0.7434618363, 
0.8877329008, 1.0443667375, 1.2128488387, 1.3926476912, 1.5832328410, 
1.7840884399, 1.9947229566, 2.2146757191, 2.4435209092, 2.6808695568, 
2.9263700050, 3.1797072430, 3.4406014299, 3.7088058696, 3.9841046430, 
4.2663100561, 4.5552600226, 4.8508154713, 5.1528578389, 5.4612866929,
5.7760175114, 6.0969796345, 6.4241143947, 6.7573734248, 7, 7 ,7, 7, 7, 7, 7, 
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,  7,  
7, 7, 7)

I've calculated the following matrices vol and volyrdc1 (obviously with the 
help of Jeff and Arun):

#Blank matrices for dumping final values

vol <- matrix( NA, nrow=5, ncol=length(volinp1))

volyrdc1<-matrix(NA, nrow=5,ncol=length(volinp1),dimnames= 
list(c("DC1","DC2","DC3","DC4","DC5"),c(seq(0,500,5))))

vol[ , 1 ] <- dcmat %*% (volini+(volinp1[1]*wt))

wt<-matrix(c(1,0,0,0,0),nrow=5)

for ( idx in seq_along(volinp1)[ -1 ] ) { 
  vol[ , idx ] <- dcmat %*% ( vol[ , idx-1 ] + volinp1[idx] * wt ) 
}  

vol

volyrdc1[,1]<-vol[,1]

for ( idx in seq_along(volinp1)[ -1 ] ) { 
  volyrdc1[ , idx ] <- vol[ , idx-1 ] + volinp1[idx] * wt
  }  
volyrdc1

My final matrix in 'volyrdc1' (kind of transition matrix model). 

Now, what I want to do is to calculate when the colsum<-colSums(volyrdc1) 
reaches a certain value and I want to get the index of the element in the 
'colsum' vector at that point. For e.g. when colsum[colsum>=18] ? It will give 
a series of cases where the condition is true. But I want index of the element 
immediately when the condition is met. In this case, the answer I want is 140 
(colsum[29] returns both value (18.63) and the character ("140") attributing 
the index). Actually, in my case 140 is year (age) when the 'colsum' becomes

Problems dealing with matrices

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